Reverting back to old Mac. How do I reinstall on that Mac

[pasta4u]

Good morning.
I am returning the newly delivered iMac due to terrible drive issues and I'm reverting back to my old iMac.

How do I reinstall my newly purchased Avast One onto that old computer. (and does it have a min. system requirement as my old mac can only upgrade to OS X 10.14?

Thank you.

[Asyn]

How do I reinstall my newly purchased Avast One onto that old computer. (and does it have a min. system requirement as my old mac can only upgrade to OS X 10.14?

Thank you.

-> https://support.avast.com/en-ww/article/One-FAQ