You have the option to save certain apps to the SD card. Not every app out there can be moved to the SD card since some apps require to be stored in the hard drive of the phone. To move apps to the SD card, you have to go into Settings > Application Manager (or Apps) > find the application you wish to move > and if it has the option, click "Move to SD card."
If its songs that you want to move to your SD card, you can either plug your phone into your computer and it should come up like a removable hard disk. You should be able to click the song file and drag it into the "Music" folder. Another method of moving any files without the use of a computer is downloading an application called "File Manager" (or any file managing app for that matter) and using that application to move files from folder to folder within your phone/SD card