The 'Link User Accounts' button is found in the Profile TOOLS section. It allows the admin user to connect an existing user with another profile, so that user can have multiple profiles.
screenshot of the location of the Link User Accounts button in the tools section
Connecting a User and a Profile
As the admin user, start typing the 'User Name' of the user who you want to add to another profile. The field will auto complete and to show a list of users who match what you type.
screenshot of the User Name showing auto complete options for possible users
Do the same for Profile Name and click Link User To Profile.
Now that user will have an additional tab in their user menu that reads "Your Profiles". Do this to give the user access to as many profiles as you like.
screenshot of the profiles that the user 'Michael' is linked to on Jamroom.net
Once a user is linked to a profile, he will be able to treat that profile as his own and be able to create any of the items on that profile that any of the other owners of the profile can create.
Unlinking a Profile
If you have linked a profile and now want to un-link it you can do so from the USER ACCOUNT tab
screenshot of the location to unlink profiles from a users account.