Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions
If you like to introduce yourself, to the community, go here:
http://lmms.io/forum/viewtopic.php?f=4&t=4480
Atm you cant use MP3, and for all what that is worth, you newer should, because it is lossy.
Wave or Ogg-Forbis is lossless and both works
Try that
Let us know the outcome :)
If it fails please post
* Name of your Operative System (Windows/ Linux/ Mac) And subtype (Home' 'Mint' '10.13' aso)
* lmms version, and the site where you got it from