Any files uploaded from your form will be sent as attachments to the email that you get. This is done automatically, you do not need to configure the form configuration for this. You can attach any number of files of any type. If you are not receiving the attachments then you should check your HTML form code.
To allow your form to send the uploaded files as attachments, you must put this
enctype="multipart/form-data" in the
<form> tag and use
method="post", like so:
<form action="https://formtoemail.com/user_forms.php" method="post" enctype="multipart/form-data">
You must also use a file input on your form, like this:
<input type="file" name="whatever">
...one for each file you wish the visitor to upload. Give each one a different name.