Assigned fields in template revert to "anyone" when using template for contract document

I began by creating a form in Microsoft Word, which I then used the "Prep Form" tool in Acrobat Pro to make into a fillable form. I brought that form into Acrobat online to create an e-sign template where I could assign fields to "prefill" and "signer." All looked well in the template but as soon as I use the template to test sending it to be filled out and signed, the assigned fields are fillable by anyone in the prefill stage, even though I had assigned them to the "signer." 

I am sure there's some small setting or step I'm missing, but having spent literal hours on it now...I'm calling out for help! 

Thanks in advance!

Kelly