All the official Oracle OIM docs: Oracle Identity Management Documentation

The OIM customisation/development sections of the documentation will explain most of those: Develop:

Lots of examples provided by the Oracle A-team: http://www.ateam-oracle.com/category/identity-management/idm-gov/

You could start from labs: How to find old OIM R2 PS2 labs?

Here it is:

Catalog:

Lab 5 - Request Using Profiles: http://download.oracle.com/opndocs/global/OIM-R2-PS2/Labs/5_Request_Using_Profiles.pdf

Sandboxes:

Lab 9 - UI Customization – Simple: http://download.oracle.com/opndocs/global/OIM-R2-PS2/Labs/9_UI_Customization_Simple.pdf

Lab 10 - UI Customization – UDF: http://download.oracle.com/opndocs/global/OIM-R2-PS2/Labs/10_UI_Customization_UDF.pdf

Application Instance:

Lab 16 - Disconnected Resources Lab: http://download.oracle.com/opndocs/global/OIM-R2-PS2/Labs/16_Disconnected_Resources_Lab.pdf

Link of having steps for customizing catalog using sandbox, may be helpful to you.

Oracle Identity Manager 11G R2 PS2 Catalog Cart Items Customization