Groups
The first task to take care of when getting started is to organise your system. Deciding on groups, roles and contacts is a good place to start but it can be hard to get it right the first time if you don't have a list of devices you want to manage as the organisation of your devices is what will likely help you decide how you want to layout your groups. Grab a piece of paper or a white board and try and group your devices in a way that makes sense to your network and will allow you to see errors they way you want to see them. This might mean your devices are ordered by location/building/floor or by some other logical grouping that has nothing to do with location. Things to think about here: a user calls and says X isn't working and you need to figure out why, what thought process would you use to figure this out and how will you want to look through groups to figure this out.
After you have an idea of what your groups are it's time to set them up, do that by going to:
System -> System Configuration -> NMIS Configuration, choose "system" from the drop down. NOTE: no spaces in names, comma separated list
If you decide to delete a group after you have assigned devices to it the devices assigned to that group will continue to be in the deleted group but the group will disappear from all of the monitoring windows. To have the devices appear again you will have to edit the device and change it to a group that exists. Somewhat analogously, if you change the name of a group each node will have to be changed to appear in the new group. Hint: if a lot of devices/groups are changing consider doing this on the command line / using a text editor and operating directly on the .nmis configuration files.