RRAS L2TP connection setup

Hi all experts

Is it possible to configure the VPN server to allow client connect only if
client have the vaild certificate?

I've setup a virtual lab, but everytime when the client try connecting to
the vpn server, it prompt the error "Do not have certificate installed".
How can i get the certificate?

My lab config:-
1 standalone CA with domain
1 RRAS server (already request the computer certificate from CA and
installed)
1 client (request the client certificate from CA and installed)

Please advice.
Thanks

BT