Apple Logic Pro /LogicExpress Discussion

I just got Logic Studio and am working on a project that calls for
various Mellotron sounds, but I could not find any such sounds in 
Logic's vast library. So, I managed to download some but I cannot find
any instructions in the manuals or on the internet explaining how to
install them. Many of the files I downloaded have .exs suffixes, but
others are contained in folders containing numerous .wav files and a
single .exs file. Still others are in folders with a single .dll file
and a correlating text file. How do I import these so that Logic will
recognize them? Thanks for any advice!