You will find empty slots around your parks. Those areas are reserved for your legendary rides. You can choose what legendary rides you want to use in each slot, according to their permanent bonuses.

ASSIGN: Tap on a specific slot to assign one of your legendary rides unlocked during the event. Select the ride you want to place there.  

REMOVE: If you tap on one of the legendary rides already assigned, you can delete it by clicking on the paper bin icon in the menu window. You won't lose your item since you can use it as many times as you desire, but it won't apply the permanent bonuses while removed. 

REASSIGN: You can relocate a new legendary ride and automatically apply the bonuses included in its description. You only need to tap on the empty slot, and then select the ride. Your decision depends on which features you want to improve at that specific moment.

Let's check some examples: 

That is how users can use their strategies by choosing which legendary rides (and their permanent upgrades) they want to use in each situation.