There are two ways to upload and manage your artwork.

If you're on your chosen product and you're ready to upload it right there and head to checkout, you can select "Upload new image/logo" under step 3 on the product page.

Alternatively, you can also go into your account, select "Artwork Management" and upload your Image from there!

Hope this helps! If you have any problems, there is an option when uploading the image to request help! (See below!)