What, exactly, do you do with hem tape?

[perpet.livejournal.com]

I've tried Google, and I'm still not quite sure how hem tape works. I want to use it to attach a zipper to a bag I've just crocheted. As far as I can tell, I put the tape on the zipper and cloth for the zipper, and then I iron the hem tape. Is that right, or do I need to still sew everything as well? Or do I (quite possibly) have the wrong type of sewing tape?

In case it wasn't absolutely obvious, I do not generally sew.

Thanks in advance for your help!