Use this inside your form. Change the input name to whatever you need. this will cause a browse button to appear to search hardrive for file. You could also add a size to it.
This sets the file size limit and "name" attribute for Bravenet's Email Forms. File attachments are only available with the Professional version of Bravenet's Email Forms. The free version does not allow attachments. If you are using a email form service from someone else, you need to check with them for the correct "name" attribute.