Connecting to database through VPN

May i please know how i can connect to a db server using pgAdmin. When i connect using putty i use a username and a pass phrase and a private key.

Below is when i connect using putty. I then login as postgres user and connect to the database.

login as: user1
Authenticating with public key "*******"
Passphrase for key "*****":

This is after i connect OpenVPN.

regards