In Universal Email 4, uploading an attachment has been greatly simplified.
1) Add a file field to your form. go to Insert -> Form -> File Field
if you use Dreamweaver to add the file field to the page, it will automatically change the forms encoding type to multipart/form-data. If you add the file field manually, you will need to make sure to change the encoding type manually.
to do this, select the form tag and then change the encoding type in the property inspector.
2) In Universal Email, Click the paperclip icon to go to Attachment settings.
3) Click the plus button to add an attachment, Click the submitted File radio button, then select the file field from the dropdown list.