You must 1st open all those 3 slots by buying them with diamonds; then you must pick the event ( three squares on right) it tells you to, click and drag that event over to the open square on the left. In this case it tells you "queue" all events, queue means in wait, so the top square (that you have clicked and dragged from the right side to the left TOP square) begins a time countdown, the event has "began"; next click and drag the 2nd event box on left to the second empty box on right,it is now waiting until event 1 is finished and will begin automatically then. Take the 3rd bottom right square and drag it to the 3rd empty box on the left, you now have "queued" 2 events to follow the 1st event. The purpose is so you can do 3 events without out coming back to that bldg 3 times, its help ful when a task asks for say 6 book readings, you can queue 3 of them in 2 bldgs and be done with the task, you just have to wait.
If you dont know, the purpose of the events themselves is so you can have more visitors & more visitors equals more money! If your your blogs are full your at your max Guests allowed, to get more guests you click the suitecase on the pier, if it turns red &asks to build more or send them away, go to your bldgs and start an event(or more like a lot of events). you'll see this will countdown your guests and then you have room and can click your suitcase to receive more guests!
Hope I helped!