How do I change the photo that is on my Link preview?

Can you please provide more details as to where we can also check the link preview?

I assumed your form was embedded on a website. Share to us the URL of the website so we can check also the actual form used.

In case you were referring to facebook page, you can fix it using the method described from here

https://www.jotform.com/answers/1371486-Facebook-Form-Link-Share-How-to-change-title-and-image-of-shared-form

Let us know if you need further assistance.