Use Windows Media Player to transfer songs to this device. If the songs are already on your computer, then use the Sync tab to transfer songs to your Mp3 player. If you want to transfer songs from CD to this player, then use the Rip tab in Windows Media Player. If this is your first time using Windows Media Player, then you probabaly need WAY more help than we could possibly give you here. Go to www.microsoft.com
and search "Windows Media Player" to get help files and instructions with pictures on how to use the software.
If you do not have any Mp3 files already, then sign up for one of the web's music services. Napster and Rhapsody are good, but the basic-level subscription will not allow you to transfer songs to an Mp3 player - you will need to get their premium (more expensive) subscription to be able to transfer songs. Limewire and Morpheus have free versions of their music service, but they are ad-filled and virus-prone.
If you encounter any sort of technical problem with the player I can help you, but read my "Tips and Tricks" on Sansa players first, as they solve as wide variety of problems.
-Tha Mp3 Doctor