Make a form in design mode and follow the below steps

Step 1:

Navigate to Options > Actions > On Form Submission > Add Action > Communication > Send Email

Step 2:

Specify Action Name, To, Subject, From, Body

Step 3:

Click on link Use Static Expression which is just below the attachment option

Specify token [File_Upload_Name:path] and at the end click on Add Attachment button

After attaching save the action