SAP ABAP Creating a field exit for a data element

I want to create a field exit for data element "SUBMI" in ECC using a program I have created for the function module. How do I activate and assign the field then exit to screen? I tried CMOD but it is leading me to "Text Enhancement" > data element documentation.

Use program RSMODPRF to manage field exits. If you've already done that and all is in order, you'll need to analyze the short dump.