Hi,
Follow these steps
1. SE80 open the webdynpro component you want to modify
2. double click or navigate to the area where you want to change ( component cotnroller or views etc)
3. select spiral symbol or CTRL+ F4 on tool bar section , it will prompt for create enhancement
4. create enhancement implementation/ short text ( you dont need to fill component section underneath it)
5. select tick symbol, it will create a text Enhancement implementation under WEBDYNPOR component
6. that’s it now you are in customer change mode, when you open methods section and scroll right you will automatically see square icons on each exit ( PRE, POST , OVERWRITE) ..if you want to create your own logic lets say preexit , double click the icon under PREEXIT , SAP automatically create a method area to insert your own code, finish coding , save it , activate it ...
good luck..
Regards
Aki