To invite multiple users, simply go to Manage > Users, click on the "Invite Users" tab and then:
Select the group they should belong to (you can change this later)
Assign them to their default location
Paste the list of emails (one per line) you wish to send invites to
Hit Send Invites
YArooms will handle everything else - your users will go through the same process they would have if you had invited them one by one.