Can't Import Handwritten Signature into Adobe Acrobat Reader DC

Hello,

I keep trying different methods but can't seem to get this to work. I, somehow, have two handwritten signatures in Acrobat Reader DC. When I go to Fill & Sign, click the Sign button my signatures (handwritten GIFs for me and my wife) show up. I can click and place in the document as needed.

I, however, cannot for the life of me figure out how to add additional signatures. I have gone to Preference>>Signatures and tried to import but it won't let me select GIFs, only PDFs. Furthermore, I imported a signature as a PDF but it doesn't show up in my list.

Any advice would be appreciated.