Audio Books on Nexus 7

[springdal2]

I just bought a Nexus 7 for my husband and am trying to set up some audio books for him.  I have downloaded Mortplayer Audio Book Player and a few audio books, but cannot seem to get them together.  The books show in the screen "My LIbrary" and I don't know where to go to get them recognized by the player.  If anyone can help me with this issue, I would greatly appreciate it since this is the reason I bought the Nexus in the first place.  My husband has vision problems and cannot read for very long and would love to listen to audio books.  I have tried 3 or 4 different audio book players with no luck there either.  If anyone can help, I would greatly appreciate it.  Thanks...