Find the system requirements and maximum OS for the Macs in your environment. I like to use MacTracker app to check maximum OS.

Once you have that info, fetch the macOS installers and deploy.

https://osxdaily.com/2020/04/13/how-download-full-macos-installer-terminal/ 

There are many options which you can find here. They all have pros and cons, I'm not listing all out here. Find the one that works for you. The simplest way is using remote command to update/upgrade. Go to a smart/static group > View > Action > Send Remote Commands > Update OS version and built-in apps > choose the version and Install Action. Option 2, I normally don't recommend third-party app since you said you're new, but you can try erase-install. Option 3, you can use softwareupdate command to download the installer like @mvu suggested. Then take a look at this POST for the installation script. 

I am a first timer too. I am wrapping up my upgrades to 12.4.  I had some prerequisites for the upgrade. All computers had to be on Carbon Black 3.6.2.110. We rolled it out to our test group and noticed that Jamf Connect was not showing up on boot, so we added another prerequisite to be on Jamf Connect 2.12. Everyone already on 12 I just force a run of incremental updates. 

So here is my smart group: 

Once I had my selection list I built the Script from erase install. https://github.com/grahampugh/erase-install

Here is the how to use it with Jamf Page. https://github.com/grahampugh/erase-install/wiki/8.-Use-in-Jamf-Pro

So you download the PKG file and in policy and then you add your script to it. 

PKG FILE:
https://github.com/grahampugh/erase-install/releases/tag/v26.0

Script I used:
/Library/Management/erase-install/erase-install.sh --update --reinstall --check-power --current-user

Appreciate that I have this setup originally also. But I forgot to add we would like to do the install silently in the backend so all the user gets is a prompt to restart afterward possibly?

Yeah I am not sure how to do that, we did it on self-service.