Completely remove that nut on top, there should be an insert that sets within that nut, sometimes it comes out with the nut sometimes it doesn't, it's a tiny sucker but what ever you do don't loose it. There will be another insert/plunger setting on top of a spring, don't take them leave them right where they're at unless you have new ones to replace them with. That spring and plunger will be underneath that ball joint once assembled. It takes some finesse but take a small screw driver and gently press down on that plunger/spring while at the same time moving it towards the ball joint. It should go together easy so don't be tempted to force it. The first few times are a real PITA but once you have it figured out it becomes a no brainer.