How do I let someone else rez/set home etc

This is done through the “Manage users” feature

Click your rental box and open the web page it gives you (either in the internal browser or an external browser)
Click “Manage Users” in the menu on the left hand side of the page
If you see the user you want to be able to rez listed, click them, otherwise enter their username in the add a user box
When the permissions record loads up, click the “false” button in the “landgroup” row to change it to true.
This will cause a group invite to be sent to them, if they fail to receive it, or their permissions already says “true” for “landgroup”, have them click on the rental box, select “Rez/Home” on the left of the page, and press the button to request another group invite.