I'm writing a book, and I feel like it would be right to include a sex scene.
Both characters are male, and both virgins as well, and I've never written a sex scene nor had sex.
I don't want it to be too detailed, and I prefer no talking, just describing how it was.
I can handle a post-sex scene, I just really need some help. How do I describe the first time? What adjectives should I use?
Are you trying to inform the reader about the characters' emotional states? Are the things they do during the scene going to be plot relevant? Are you trying to entertain or titillate the readers?
Once you know what you are trying to accomplish, you can figure out how you will achieve those goals. Choose adjectives and descriptors that will emphasize the mood that you wish to convey, and draw attention to the aspects of the scene that are important.
And if you can't figure out what the scene is adding to your story, maybe you don't need it at all. A fade to black that cuts straight to the pillow talk is perfectly acceptable if that is where the important details of your story are.
Don't worry about seeming foolish, just write a draft of the scene anyway. Share the draft with acquaintances who have had the experience you want to describe, and ask for their advice. Listen closely and make note of phrases and details that make the scene more authentic. Then, rewrite the scene a few times and consider it done. Never disclose your sources.
I'll preface this with the caveat that I would recommend that given you're working in a YA readership, and not simply because it's a sex scene between two men. That said, you might want to consider a "Fade to black" before the sex of your sex scene actually happens. The reason for this is that Erotica and YA rarely cross the same genre (and even then, they are rarely sold in the same stores). Even stories written for adult readers avoids descriptions of what someone is physically doing during sex in favor of metaphor and emotional consideration. While content of books are able to get away with a lot more than tv or film (parents are just happy the kids are reading something, rather than getting in trouble with the [insert new form of media distribution here] that is all the rage with kids today (fun fact, back when mass printing and distribution of books was a thing, parents were worried about their kids reading to much. Forget what you heard in "Beauty and the Beast", parents thinking the kids these days are too into new media and will bring about the fall of civilization is the real Tale as Old as Time!).
Another way to approach the scene is to be rather unhelpful in indicating if the sex scene was even a sex scene. To point to a famous example, there is a scene in one of the later Harry Potter Books (I believe it was either Book Six or Seven) where there is some fan speculation where Ginny engaged in Oral Sex with Harry. The wording is unclear in the actual text (which says that Ginny kissed Harry in a way he had never been kissed before implying it was more interment than Harry's past romances, and that shortly after the pair finish whatever they were doing, Ron (Ginny's older brother and Harry's best friend) enters the room and is oblivious to just how awkward the others are as he kills the mood.). Given the audience size and range the books had, if the fan theory is what the author wanted to happen, then it's likely she use a high degree of coding to get around the issue... those with dirty minds or prone to reading in-between the lines would get it, while parents had an out and younger children would have no clue. If it was just really hot kissing, than it was just readers with a dirty mind reading way too much into the situation (since the scene was ultimately humorous in the end, either read serves the intent and the humor is preserved. Being almost caught by your best friend/older brother, who is clueless about just how close he came to catching them, is the point).
At either rate, what Ginny and Harry were doing in that moment had no relevance to the plot, and thus not too much detail was required. Additionally, keep in mind that a fair few people might be a little grossed out by the scene of two characters who might be minors are getting it on in graphic detail. It also helps you since you admit you have never had sex in your life. Since you're ending the scene before the climax, you don't have to wonder if you got it right. My advice is to end the scene some time before the characters drop their pants (at most do the written word equivalent of a film having an ankle height camera shot of the pants hitting the floor... imply what's about to happen, but don't actually show it.).
If you do want to go into graphic detail... I mean... you know researching that on the internet is like... ridiculously easy to do... Though make sure you do more than look at gay porn, as porn of any type is not the most accurate depiction of sex (as a former pizza delivery guy, I can tell you that the job is not as interesting as the porn industry leads you to believe.).
