When you first sign in to the app, you will be presented with the "Trending" page.
Click the Hamburger menu on the top left and then click "Add New Artwork".
When adding an image, you have the option to add one already on file or snap a photo of your artwork using your camera.
You can then enter the description of your artwork. If you have the Pro Account, you will be able to set the visibility of the project.
Currently, you can only upload images. Support for video embeds, Marmoset Viewer, and Sketchfab is only available on desktop.