New iMac; Where is the "Tips" app? I am lost without it! :(

System Preferences > Notifications > Tips > Allow Notifications and set Alerts in case you want the tip to hang around until dismissed.

There is also the macOS User Guide which can provide more info on using your new iMac.

There are also Help tips and tutorials for each of the App's that you are using. Learn the Basics is in Finder Help.