Go through the initial installation sequence: Location and accessibility; WiFi; Migration Assistant for transferring data (only if appropriate — you might want a clean installation); Apple ID and login. Etc. From the Make This Your New Mac screen you can customise settings as you wish.
If you want, auto-hide the dock to get more usable screen space (the dock is the strip at the bottom of your screen that shows applications): In System Settings, go to “Desktop and Dock” and switch on “Automatically hide and show the Dock”.
Make the monitor display denser and hence win more effective screen space: In System Settings, go to “Displays” then click on “Resolution Scaled”, and click “More Space”.
Install and activate cloud storage, like Dropbox, OneDrive or iCloud (your files will then start downloading).
A personal recommendation: From the App Store, I install Flycut for clipboard (copy-paste) management and Magnet for workspace (windows) organisation. You might need to Google how to use these — very easy.
Restart your computer then ensure that your cloud storage (for example OneDrive and Dropbox) and Flycut and Magnet (if you installed them) have icons in your Menu Bar (the Menu Bar is the strip at the top of your screen). If not, then go to the Preferences in the missing (from menu bar) applications and ensure that Launch at Login is ticked.