The other posters are correct to ask you which CPL you are referring to. CPL is a system, really, and it includes many neighborhood libraries (fairly small but nonetheless full of great resources), fewer regional libraries (which are quite large) and then the enormous flagship location, which is called Harold Washington Library Center (HWLC). HWLC takes up an entire city block and is bordered by State Street, Plymouth Court, Van Buren Street and Congress Parkway. If you are taking the Red Line, you can take it to the Jackson stop, then walk a few steps south (not even one full block). You do not need to transfer to the Brown Line or any other line.
The Rogers Park and Edgewater neighborhoods (Loyola's main campus is in Rogers Park, close to Edgewater) both have their own neighborhood libraries.