RedBubble is very simple, but you will not be able to make any changes in the designed products.
You will start with the page below.
(The look of the pages will vary with the time, as I add new designs)
You can chose from the sub-categories in my shop, then you will see the available designs.
Click on the one you want. Below the big picture there is a list of all items available. Again, click on the one you want – and the rest is just following the instruction of Red Bubble.