You can upload an artwork by going to the dashboard on your profile. You will find the “Upload Artwork” button there.
To edit artworks, just scroll your mouse over the listed artwork in your portfolio, and an option to click “Edit”, “Preview” or “Share”. Clicking “Edit” will take you to your “Edit Artwork” page, where you can upload a new image or any text in there.
To delete artworks, go into “Edit Artwork” and scroll all the way to the bottom to delete the artwork.