Need to add a new field in OAF by using Extending the View Object. This docement might be useful.
In this Document you will learn from a working example, how to extend view object in OA Framework to add a new field to standard page. This article will also teach you how this extension can be tested from both jDeveloper and also how this can be deployed to eBusiness Suite.
Extending view object by adding new field in oaf 2011-04-15
Extending view object by adding new field in oaf