how to turn a VPN

The MacOS user guide explains it in detail. Its pretty similar across different versions, but you can select which OS you're on and it will show you the instructions.

Set Up a VPN Connection on Mac: Set up a VPN connection on Mac - Apple Support (MZ)

Side note, why do you need a VPN? They're unnecessary for most people, and like BobTheFisherman said, if its through work, have your IT department configure it.

1Key1 wrote:

How to turn on VPN

First question is why do you need a VPN? If the VPN provides a secure point to point connection to your company or other organization's network, contact the network administrator/VPN administrator and ask them how to best configure your VPN client to connect to the network.