MOVED: how do i set up a settlement or is it possible to

Your friend can spawn in to your world and set you as an ally and then come to you and place a bedroll in your base. Once done it is now a settlement for the two of you.

You cannot currently designate your base as a spawn point for new players joining your game. They have to place a bedroll in order to make it their spawn point.

You could go into the game files and remove all but one spawn point and then change it's coordinates to match where your base is but if you don't want to mess with the files then your friend will have to journey to you.