When creating a subscription in SQL Server sometimes the following error will occur:

The remote server "%s" does not exist, or has not been designated as a valid Publisher, or you may not have permission to see available Publishers.

The error is pretty straightforward and indicates that the replication agent login used to connect to the Publisher is not a member of the publication access list (PAL).  That would be the Distribution Agent process account for Transactional Replication and the Merge Agent process account for Merge Replication.  Add the agent process account to the PAL and try to create the subscription again.