Go to the tag database, make a new tag, assign it to the PLC tag, enable the alarms, set the conditions, save the tag, go to the FTView SE Command line, and type "AlarmAcceptEdits" or restart the server.
You can also use the much nicer (but seriously buggier) FTAlarms and Events, which once set up would not require making changes to the FTView application at all. That is a whole different subject though.