There should be an example implemeting called /TRMKR/SEC_CUST_DATA
I think you have done everything right, but make sure you activated your enhancement afterwards.
You see that in your sreen. I think there is something like saved/active or something like that.
If done everything right, transaction FWZZ should show a new tab
IF that doesn't help yu out you have to share a bit more details about what is not working.
Regards
Florian