If an adopter is not with you in person, we highly recommend using the credit card checkout because that flow puts the e-signature functionality on their phone.
If the adopter does not have a smartphone: The checkout can also be sent via email by clicking "customer has no phone" (beneath the field with the phone number). You can then copy/paste the URL of the new tab that pops up into an email to the adopter.
If you would like transactions emailed to your adopters automatically by default, please email firstname.lastname@example.org to have this feature enabled on your account.
You can read more about processing transactions here: How do I process adoptions (and other transactions)?