You can't... but "use local font" wouldn't help you in this case anyway.
Because filling a form is considered "authoring" in that the entire font needs to be embedded for it to work correctly, only fonts with the right license can be embedded for form filling. Checking "use local font" will simply tell Acrobat/Reader that it is to use the local system font for fonts with the same name rather than extracting the embedded font. It has nothing to do with form authoring.
Thanks for getting back to me, Joel. I thought when you select a font to use it automatically gets embedded so the user will then see the document as it was created and not change the appearance. I tried to view my doc on a different computer and so I get the message I mentioned in my previous post ("Helevetica Bold cannot be used"). So my question is, what do I have to do to get the fonts I used to embed?