Restoring two Time Machine backups to two partitions

My iMac's hard drive crashed and has been replaced. On the drive I had two partitions: one with Ventura, the other with Mojave (so that I could run older programs, especially iWeb). I have Time Machine backups on an external drive. It kept two backups, one for the Ventura partition, one for the Mojave. When I started up the iMac I went to Time Machine, and it asked which one I wanted to restore from. I restored the Ventura back-up.

Now I want to again create a second partition on the iMac, and reload the Mojave back-up to that partition. How do I do that???

Thanks!