Bought a skethcup Pro subscription licence, but how can i activate my 2018 licence with this?

Just bought 2x sketchup pro subscriptions. Our projects are still in sketchup 2018. How can i use this subscription to activate a sketchup pro 2018 licence?

Subscription is only for 2019. If you need to keep the skp project file as a 2018 version for collaboration purposes, you can always save back to the 2018 version.

With @eneroth3’s legacy save extension you can easily back-save to the same version as a source file even without remembering what it was.

If you already had 2018 licenses you should simply continue to use it if you’re not ready to move to 2019. Your 2018 license doesn’t expire, and is good for as long as you want.