When you do a restore it should say do you want to do a backup, say yes (if you havent done one that day) and let it do its thing. Then after its all restored you get the option as if it was new to start a new iPhone or restore from backup (and then you get a choice from the drop down box), choose the one you want to backup from and let it do its thing again.
Depending on how many apps you have etc and how much music, the longer it will take.
Hope this helps
Ben