I assume you want to view this on the server, I also assume that this is a linux server, since no OS was specified, and no config was posted.
To view connections on a linux based OpenVPN server, have these lines in your config:
# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status openvpn-status.log 5
status-version 2
Then from a command prompt run this:
cat \etc\openvpn\openvpn-status.log
The output will contain line(s) like this:
CLIENT_LIST,cert-name,CLIENT SOURCE IP:63407,10.8.0.250,81568,99077,Wed May 30 05:11:19 2012,1338372679
Your client IP range is defined in your server.conf, so your client IP may be different, in the example above the client IP is 10.8.0.250
