I am having trouble adding a PayPal link to my form

Are you trying to integrate PayPal into your form? I checked your form and I can see that it is not yet configured. Here's a screenshot:

Please refer to this user guide on hHow-to-Integrate-Form-with-Paypal.

If you want to insert an external link in the form, please check this guide.

Hope that helps. If you have any questions, let us know. Thank you.