Allowing to log into domain of different Subnet

[sanju_3400]

Hi, I am equivalent to administrator of my network, We have 2 offices worked on diff subnets. means one office ip range is from 135.51.20.0 to 135.51.20.255

other office range is from 135.61.20.0 to 135.61.20.255. We have PDC server in 1st office ip-135.51.30.288 , ads is loaded there. We want 2nd office peoples also to be logged in the same server. i have heard that it's possible. What entries should i made in host or any other file? pls tell if u know.