Currently Being ModeratedMar 31, 2012 7:43 AM (in response to mamaruca)
Copy the backed up iTunes folder into the Music folder of your new profile then install iTunes. If you have already installed iTunes rename the current iTunes folder as something like iTunes (Empty) or just delete it.
See this User Tip for an easy way to keep the backup up-to-date in future.
If you'd rather restore your library to a non-standard location see: HT1589: How to open an alternate iTunes Library file or create a new one