How to use the inventory of boosters in my profile I have won.

To use boosters in your inventory you need to tick them on the pre level screen. Not all the boosters will be available to use on every level. The fishes, lucky candy, and coconut wheels are not available on every level. So on my first screenshot I have the option to play the lucky candy, whereas on my second screenshot I can play the fishes. Note I have timed colour bombs from the daily treat machine on both pictures.

To play the fish now, click on it on this screen and a green tick will appear. Don't forget to untick at the next level to save your boosters for the harder levels.