9/22/2015 Update. I have a few designs on this site, but I have not sold anything at all in the past year.
This is by far, the easiest site I’ve used so far. Plus they have very comprehensive and clear instructions written out. Nice job RedBubble!
CREATE A SELLER ACCOUNT
1. Click on Sell Your Art at the top of the page.
2. Click the Red GET STARTED, ITS FREE button.
3. Select your username
4. Confirm your account by going to your e-mail and clicking the confirm link.
5. Click on Payment Details and fill out the form.
6. Click on ADD NEW WORK
ADD A COLLECTION (This is where you organize your work)
A. Go to your portfolio page (Click your Profile and then look for the tab that says Portfolio.)
B. Click on the Red Words New Collection