Use the “+ add” menu in the navigation bar. If the artist is already on Bandcamp, choose “existing artist.” If they’re new to Bandcamp, choose “new artist".
You can also give the artist access to their page later – just roll over their image in your artist grid, and select “give access”. This will let them add their own items and edit the page design. Artist-paid items do not show up in the label's discography.
There's also a "remove" link should your relationship come to an end and you wish to transfer the page and its contents over to the artist. Artists will then be able to change the payment recipient on the previously label-paid items, but we'll shoot you an email if that happens.