What You'll Need
- Some sort of photo editing software ( Photoshop, Gimp, Pixelmator, etc )
- Blank t-shirt templates. Here are a few to choose from:
How To Git 'Er Done
Create a new document that's exactly 800px by 400px. If it's not that size, your design will be rejected without even a second thought.
Next, import the design and the t-shirt template into the new document. What I tend to do is duplicate the design at this point. Position one of the designs over the shirt template, and size it to fit. The other I use as the background to the document itself. You can get creative here and add your own texture or flare.
Often times, there is a special layer on the t-shirt template that you need to put your artwork on. That is so the shadows and highlights are applied to make the mock-up realistic.
Save the document as a jpg and upload it.
That's about it! There are a few other details that you can apply to the mock-up that I'll cover at another time, but this should work for now. Cheers!