How do I get the link to a photo so I can add it to my form?

Well, the question pretty much sums it up! THANKS! 

You can use Image field to add image to your form. 

If the photo is on your computer select Upload Image file option and if you have image of your photo on a web then select Enter URL option. 

You can also check this guide: 

https://www.jotform.com/blog/13-More-Options-for-Adding-Images-to-Your-Forms 

In case that you have photo on you computer and you want to create link of that image, you have to upload it to a website first so that you can get a link that opens your image thorough the internet.

Here is a great free resource I would recommend where you can upload your images and get the URL - http://cloudinary.com/ - there is a free plan I think you can work with. 

Another option is to work with dropbox.

Hope this will help. Let us know if you need further assistance.