Domain Trusts

I have two domains connected over a WAN. I need to setup a two trust between the two. When I try to add domain B to domain A, I get a message that it cannot find the domain controller for domain B. Is this an issue where I’ll have to place an entry into the LMHosts file, load into memory, and then try to establish trusts? Whatever the answer, please give me the details so I can do this.

Thanks…Tom.