Lets say I have Domain A which currently is set up with my SharePoint environment. We have merged with Company B. We want Domain B to work with our SharePoint environment. So they can log on an browse. What would the steps that we need to take to make this happen. We are using Claims based authentication.
By "want DomainB to work" I assume you mean that you want users that are members of Domain B to be able to log into SharePoint. To allow this I believe you just need to have Domain A trust Domain B. This assumes you are using NTLM or Kerberos accounts and not a Trusted Identities.
You would also, of course, need to make sure that you gave access to the appropriate AD groups. Using "All Authenticated Users" should get the job done.