This is one of the rare pinball fx tables where you do not have to know what you are doing to unlock the achievement, but in case you want to know how here is your solution...
To unlock this achievement you need to activate the Whirlybird Mulitball which you do in two steps
Step 1 (have lots of fun...)-
On the table there is a ramp above a clock; above the entrance to this ramp is a board which toggles though the ramps four game modes before you launch the ball. If you look at the clock you will see the game mode changes on the hour, so aim to launch your ball around the half hour mark when the board is on the 4th option, which should lock the 1st/multiball option by the time the ball gets into play.
Step 2 - Once you have the board in the correct position just get your ball up the ramp a total of 5 times, once to activate the ramp, once to activate the mode and then 3 times to lock the balls. Once you have done that then the achievement will pop.
Good luck though this is an easy one.