You can upload a design after choosing a product from the catalog to customize it using the mockup generator, or simply add a design to your design library for later use. Find instructions below:
From Mockup generator
Find an item in our Catalog and upload your own design under "Your Library". Designs uploaded using the mockup generator will be saved to your library so you can use them on other items in the future.
From Design library
From your Profile, click the Your Library tab, you will be taken to your design library. You can then click the "Upload Designs" button and choose to upload a design from your device or from an existing URL.
After your design is uploaded, you can Edit it to add a design name, tags and category.