Control towers are super easy to install. Make sure your landing pads are equidistant on each side of the car to make them line up.
When mounting Control Towers, place the towers loosely over the crossbars and set the towers into the bases before tightening them to the tower. Measure your bar that will extend outboard of the tower equally on both sides, and then tighten them down.
On any tower system, you should add your endcaps last.