How to create a group (Just Survive)

Guys, I ran into such a problem, my friend and I bought a little money, but what's the point, if I make a platform, he can't place anything on it, the output needs to be entered into private somehow, how to do it? I didn’t find anything sensible on the Internet, here is the /squad invite option, but when leaving the game, a friend cannot build anything on the territory I built earlier