Here's how to setup VPN on a Chromebook using L2TP-IPsec

Below are the steps :

Right-click on the clock and choose “Settings “
Click on Add Connection and then choose “ Add Private Network “
In the pop-up windows, enter the below details :
- Server hostname: the server addresses you will find here
- Service name: LimeVPN L2TP
- Provider type: L2TP/IPSec + pre-shared key
- Pre-shared key: private
- Server CA certificate: Default
- User certificate: None installed
- Username: LimeVPN account name
- Password: LimeVPN account password
- OTP: (leave blank)
Click on Connect and you will be connected to VPN.
If the connection does not work, first please make sure you are using a regular, standard VPN server
If that does not connect, try changing the connection proxy settings. Try both “Direct Internet connection” and “Automatic proxy configuration”

Which device do you use?