it is the same process of other infotypes which you add, ie adding the structure etc,
Please follow the standard infotype and refer the cutsomisaiton in SPRO
check the
http://help.sap.com/erp2005_ehp_05/helpdata/en/38/ fd1f7ed337404cae5c8a2341dbdca4/content.htm
Adding any Info Type IN ESS in EHP5/6 through WebDynpro Configuration