When signing up to Bluethumb, on the initial sign up page you will be asked to sign up as either a Collector (a art buying account) or as an artist (artist selling account).
Sometimes people miss this option and accidentally sign up as a Collector instead of being an Artist. If this happens don't panic, there is a simple way to switch your account over.
When logged into your account hover over the top right where it says "Hello YOUR NAME!" and you should see a drop down menu appear. From this menu you should see, as the 8th option from the top, "Become an Artist", click this.
You will then be taken to a page to create your artist profile. You will need to fill out all the mandatory information and click "Save" at the very bottom of the page before your artist account can be created. Please note you can edit this information at any time in the future once the account is created.