Hi Liz...
simplest way should be - plug in your mp3 player to your pc (or f it has removable memory insert the card) which should show up in
'This PC' - open it, then copy and paste the required music files to a
temporary (new) folder in
'Documents' (don't put them in 'music' - you might mess up your music library!)
Next step disconnect your mp3 and plug in the second player (as above) - copy and paste the files to that, and test to make sure it has worked correctly. If it has you can then delete the temporary folder from your PC.
Cheers, Ric.
(In theory if you have two ports available you could plug in both devices and copy directly from one to the other but the method given reduces the risk of a mistake!)