To join queue you have to click in your profile picture, green means in queue and red is not in queue
Every 5 minutes the queue will "throw a dice" in the server side, if the number is equal to 5 the player will receive a contract, if not, it will need to wait another 5 minutes for a new chance to get one. This is made like this to not saturate the server giving contracts to everyone.
In the leaderboard tab you can see a full list of all the users who have used the Boosting App, you can filter by better timing, most hacks, most deliveries or most EXP
By default, a best time of 15 hours is given to users who never have completed a contract to force them to go down in the list when you filter it by time.