How to start with CiviCRM and creating an extension to add Contact Tab in PCP
You can find instruction on how to create an extension in the CiviCRM documentation here: https://wiki.civicrm.org/confluence/display/CRMDOC/Create+an+Extension

I would recommend you first think about:


what hooks are you going to use (check https://wiki.civicrm.org/confluence/display/CRMDOC/Hook+Reference)
what API calls are you going to need
do you need to create new pages, forms, reports or API's?