Open the terminal, and enter these commands to install the latest version of SoftMaker FreeOffice:
cd Desktop/
wget -c https://www.softmaker.net/down/softmaker-freeoffice-2024_1218-01_amd64.deb
sudo apt update
sudo apt install -f ./softmaker-freeoffice-2024_1218-01_amd64.deb
If you already downloaded the SoftMaker FreeOffice .deb file, you can change directories with cd to the directory containing the .deb file that you downloaded, and run the last two commands from there. If you already downloaded either the SoftMaker FreeOffice .rpm file or the .tgz file, those aren't the right files for Ubuntu (they're too complicated for a new user to install), and you need to download the .deb file instead.
Alternatively you can run the following commands to configure SoftMaker FreeOffice to be updated automatically like the rest of your installed apt packages.
sudo -i
mkdir -p /etc/apt/keyrings
wget -qO- https://shop.softmaker.com/repo/linux-repo-public.key | gpg --dearmor > /etc/apt/keyrings/softmaker.gpg
echo "deb [signed-by=/etc/apt/keyrings/softmaker.gpg] https://shop.softmaker.com/repo/apt stable non-free" > /etc/apt/sources.list.d/softmaker.list
apt update
apt install softmaker-freeoffice-2024