Step 1: Login to the cPanel.
Step 2: In the Advanced section of the cPanel home screen, click MIME Types.
Step 3: In the MIME Type text box, type the MIME type that you want to add. For example, type application/pdf.
Step 4: In the Extension(s) text box, type the file extension or extensions that you want to add for the MIME type. For example, type mypdf.
Step 5: Click 'Add' button to complete the setup.