Adobe Fill & Sign for iPhone

I have a PDF form with numerous fields.  It is was created using Adobe Acrobat DC Pro as a form.  What I mean is, they are Adobe PDF Fields, not just emty spaces on the document.  I also have a Digital Signature.

It seems that Adobe Fill and Sign prefers to CREATE and Fill fields.  But that is not what I want.  I want to Fill already existing fields. How do I do that?

I have no problems with the digital signature part.

Device is Android Phone