Accessing a Linked server
A linked server is referenced just like you would reference a database, with multi-part naming - LinkedSvrName.DBName.SchemaName.ObjectName.  There isn't really anything else to "accessing" a linked server.  

There are some settings you will need to be cognizant of to ensure you can return data; RPC and RPC Out for instance.  Also you will want to use linked servers sparingly as performance will suffer.  This should get you well on your way to Googling the rest of what you need to know.  This topic is really too broad to be covered in this format.