All you have to do is go to the "My Account" section and tap the thunder-shaped logo just below your picture, on the right - you will be offered to ”boost your profile”. If you tap this button but you are out of Boosts, a popup will explain how this feature works; if you continue, you will be redirected to the shop. If you do have Boosts, the number of remaining boosts that you can use will be indicated. In order to activate them, you will just have to click on the Boost button and then your Boost will start and the remaining time that you have (out of 24 hs) will be indicated below. You can also purchase or use Boosts directly from your Main Page: just click on the thunder-shaped icon on the bottom left-hand corner.
Boosts make your profile one of the top ones around you during a limited amount of time. This means your profile will be the first one active users (that match your preferences) will see on their home page when they log on.