When you click on a player, you will see a red 'Invite to Order' button. You must be a Counselor.

If you are not, you will only see the grey 'Block' and red 'Add contact' buttons.

Note that there is a gotcha: if they have already been invited, you will not see this. And likely they can't find the message that had the invitation in it any longer. You have to go to Order / Management / Requests to Join - reject them.

- then you can go back and re-invite them.

(This happens a lot.)