You start by reading Chapter 2., Restore Procedures – General Information, of the Backup and Recovery manual, ideally for your version of the operating system.
Exactly what will be done will depend on equipment, the models of your systems, the versions of their operating systems, possibly the PTFs that you have installed, and perhaps other details. Mostly the steps will be the same regardless of which version of Backup and Recovery that you refer to.
It might vary greatly depending on the meaning of your question —
…restoring a test box to look like production box from a monthly backups…
A few details might be helpful. In particular, is this a one-time restore from one of your monthly backups or are you thinking about doing this monthly?
Do you really do a monthly SAVSYS? Do you have a reason why? Or is it just because you can? (There’s nothing wrong with it. It just isn’t valuable to do.)
A lot more comments are possible after more is known of what is being done.