can't access other sound library

I recently upgraded my laptop to a MacBook Pro from a windows model therefore I am relatively new to Garageband.

I had a library of sounds and effects from previous music software on my old laptop that I have transferred to my new one, however I don't know how to access them using Garageband, the old software in question is Native Instruments.

Is there a way I can use these sounds and effects through Garageband? I have about 10G of sounds unused at the moment!

By the way I am using the newest edition of Garageband