How can I add pictures to my products?

My suggestion is to check this guide: Setting Up Your First Order Form

On the step 5 of the same, you can see how to add the name of your product and its price.

Right under the same is the field where you can add the link to your image.

Once you do just click on Save Product and that is it :)

This is a screenshot showing the same field:

Do let us know if you have any additional questions and we would be happy to assist with the same :)