Click on that event so you can see what MIB file it is (last field under "Trap Details"
Go to Options - Events - SNMP Trap Settings
Select the MIB you need
Find the event you want to change...
You can one of two things here
- disable it (set the Enable Trap Handling value to No)
- Change the severity to something besides Warning (informational, etc)
I usually don't disable trap handling unless it is complete junk (authentication traps, etc)
This is possible only for SNMP traps..