Hi! This can be confusing at first but it's simple once you get it done the first time. When a person joins your party, their rank is usually a recruit. You are able to promote them in the party with /p promote (username) which would change their roles. Doing this 1 time will change them to normal member, 2nd time moderator, 3rd time co-leader.
In /p perms, there are a list of tools which can look intimidating. Once you promote your friend to whichever role you want, find the tool named with the same role on the /p perms page and click it. Here, there is a page of glass. When you hover over them there are corresponding permissions to build, break blocks, claim land, open chests, etc. Left clicking these turns the glass Green (Giving them permission) or Right clicking which turns the glass Red (No permissions to use.) You can customize these permissions for all roles in the party (recruit, member, mod, co-leader) to how you like it!
I hope this helps.. and didn't make it too confusing for you. If you ever need help let me know on discord, or in-game!
-Madison <3