Please read the user manual if you have never used SNMP or the dude before. This tool can easily over run the CPU on your network equipment if you get it setup wrong.
First until there is a good understanding of how Devices and Probes are automatically added do not use auto-discover.
Manually add a device, make sure they both contain the same SNMP Community. Add a link between devices, select SNMP in the link settings, Pick the device and the link you want to monitor between the devices.
As an example your router board 10.0.0.1 and your computer 10.0.0.198, double click the link between them, in Device select RB133, in Mastering select snmp, in Interface select the Interface on your RB133 that is connected to your computer, leave Speed blank, in Type select fast ethernet.
Please read all this stuff has been posted many times.