Time Machine won't let me restore the current files

I recently went to downgrade to Sierra, and backed up my hard drive before resetting it, the name of the drive I was on was "Macintosh HD Old" there was also a drive named Macintosh HD also on the computer. When I try to restore from the Time Machine, it will only let me restore from the one named Macintosh HD, and not the one I need to restore from, Macintosh HD Old. How to I get it to restore from the one with the different name? I rename or delete contents from the Time Machine, cause it says it contains backup files, which is true.

please help fast.

-Charlie