Hi,
I wonder which certificates you are referring to, since neither PPTP nor L2TP/IPSec use any.
So for PPTP it is sufficient to enter a name, the servers dns name, your username and password and then connect.
For L2TP/IPSec it's almost the same, except for the PSK which additionally needs to be entered in the field "Shared Secret". You can get the PSK for the server(s) chosen from the server page in the Member area using the button "IPs/Ports".