@otrott, I hope you’re enjoying your journey on EndeavourOS.
You can search packages with this command in terminal:
pacman -Ss <package_name>
For example:
[triby@eos ~]$: pacman -Ss featherpad
# Output for that command
community/featherpad 1.1.1-1
Lightweight Qt plain text editor
With that output you know that the package exists on repositories and can be installed:
[triby@eos ~]$: sudo pacman -S featherpad
Other way is to use yay as @dalto suggested in his answer, but, wait a minute, you can also use pacseek for search, select and install packages.
Very important: Before installing software, please be sure your system is up to date by executing yay (no parameters).