Hey JoaoPaulo . Happy to have you over here.
You can install flarum only if you have ssh connection available. Soon, during a stable release web-installer will be available. So, for now, make sure you have ssh connection to the server and try to follow these steps. https://discuss.flarum.org/d/1951-a-flarum-installation-guide-for-dummies-and-the-truly-clueless
And, if you are on a shared hosting, then install flarum on your computer then move that to your shared hosting account via FTP. Make sure you've run all the composer commands too. But hey, that takes a shit load of time if you have serious slow upload speed ?
