You first have to use TiBkp to back up your files. Then you can restore what has previously been backed up.
But you haven't given us much to go on. Why do you need to restore? What files are you trying to restore? TiB backs up programs and settings by default. I don't believe it backs up files stored on your internal or external SD card.
Where you back up your files to matters, too. For example, if you put your backup files on the internal SD, then do a factory reset, your internal SD gets wiped out, and so will you backup files. Back up to an external SD card, or copy your backup files to a computer for safekeeping.