how do i add the SSL logo

If I understood you completely, you would like to add a logo to your form? All our forms including any uploads are SSL secured: https://www.jotform.com/blog/175-All-Forms-are-Now-Secure-by-Default-The-SSL-Limits-on-Free-Accounts-are-Lifted-

So you can upload the logo by using regular image field:

If you had something else in mind please let us know.