Help with a New Users Setup

[SethTGM]

I have been charged with getting some metrics on our network from the boss... I'm fairly new to snmp and to Cacti. So let me give you a quick rundown of my accomplishments so far:

Setup a linux box from an old workstation to run cacti
Setup cacti and it pulls the localhost, and able to pull SNMP data from our exchange server...

Thats it so far...
Now my problem is we have a few SNMP managed switches we want to monitor so we can figure out if we are having any latency issues or problems at night. They are both dell powerconnect series.
I can get them to connect and pull the snmp - interface query fine. I cant for the life of me get a damn graph to work and show data. Could someone maybe either direct me to some info on snmp that might tell me what everything means or possibly tell me what type of graphs i have to setup to monitor traffic on these switches?

Thanks,
Seth