Q: How can I get permission to see my own back up on a new computer?

Hey

My old Macbook Pro crashed, but happily I just managed to back up, using time machine before it happened. Now I've bought an old iMac and I want to see some of my old documents from the back up from my old computer, but here is the problem - when I press either documents or desktop I get the message "The folder “Desktop” can’t be opened because you don’t have permission to see its contents." How do I get permission to see my own back up??

I hope you can help me:)