Before we get into details, let’s look at the brief steps for implementing this requirement
1. Define your Custom Measure by giving this a label.
2. Modify pl/sql package PJI_FP_CUST_PJP0. As the name suggests, Oracle expects this package to be customized. Effectively this is a custom hook
3. Personalize the Project Intelligence reporting tab, to add desired custom measures.
These are demonstrated in the Document.