Hi Diego,
for adding the new field in the WD component following steps are required:
1. create the append structure to RCF_S_CAND_PERSONAL_DATA_PL and define the new field
2. Create enhancement implemenation to WD component ERC_C_CAND_OVERVIEW_UI
3. Add the new field to the "Context" of the componentcontroller; rightclick and create via wizard
4. Update new context mapping in the view V_COMMUNICATION and Context Tab (rightclick on right context folder and "update mapping")
5. Add new field (label and input field) within the layout tab at the right place
6. Bind input field with new context element/attribute
Well, the demo is too simple. It covers just some aspects and contains the implicite enhancement way. In Web Dynpro, enhancements are done as explicite enhancements, means Pre-/Post-/Overwrite Exits of WD methods.