Once you have an account go to “account” > “OpenVPN / IKEv2 username”
Copy the username and password
Unzip the files and choose any server that you want to use (like us-19 or similar)
Edit it in the Text editor app (it’s a built-in Chrome app on Chromebook) or any other text editor
All the way at the end, after "TLSAuthContents": "-----BEGIN OpenVPN Static key V1-----" put in:
,
"Username": "(Put your username here)",
"Password": "(Put your password here)"
You can just copy and paste it and you’ll get the right formatting.
Make sure that you start the paste right after the end quotation mark.
Save the .onc file
Upload it to chrome://network#general all the way at the bottom where it says “Import ONC File” (don’t worry if you don’t notice anything, just try scrolling down a little more and it should say Networks imported: 1 regardless of how many you actually imported)