Try this : you need a text object, and a global variable called 'tickssofar'
+ System: Always (every tick)
-> System: Add 1 to global variable 'tickssofar'
+ System: Every 1000 milliseconds
-> Textfps: Set text to "FPS: "& global('tickssofar')
-> System: Set global variable 'tickssofar' to 0
This is not my creation ( i can't remember who posted, so can't credit them)
(should be on newts snippet widget)