Muslitple AD domain configuration in BO 3.1

Currently, we have AD domain a.com and 2000 users are added to that. it's working fine. Now we have acquired another company, they want access to our GDW. So we want to add a new domain (b.com) and a new set of users into that group. We have created an AD group b.com, then I have added the new group details into kb5.ini file. A new secwinAD group has created. Added the new group details into CMC, a group also added without any issues. But after that, no one is able to login into BO 3.1. please let me know how to add a new group in the multi-forest design