How to transfer purchased songs from the itunes store into your library?

I had bought some songs off of itunes, and when I downloaded the new software for my itouch it got deleted off of my touch and library, but in the itunes store it says I have it purchased. How do I get it back into my library?How to transfer purchased songs from the itunes store into your library?
Hi,



I recommend a very professional ipod transfer.



http://www.topmediasoft.com/ipod-transfe鈥?/a>



With it, you can:



1: Transfer/Share iPod files from one iPod to another iPod.

2: Transfer/Backup iPod files from iPod to your computer.

3: Transfer/Backup iPod files from iPod to your iTunes.

4: Manage your iPod like a movable hard drive and transfer ipod videos/photos/music between iPod and iPod, iPod and computer/laptop, ipod and itunes.