After your brother's death, you lived with your uncle's family. When you get there and you decide to rest, a dragon and a unicorn come to your dream and ask for help. If you agree to help them, they will lend their strength and charm to you, to help you carry out your "task".
In order for you to be able to install this game, you need to enable (allow) installation of applications from unknown sources (Unknown sources) in the phone settings. Usually this item is in the Security section