rahul rahul I will try to give you a quick summary:
Create your database in MySQL (All hosting allow you to do this). I recommend MariaDB if possible.
Once you have it done, run your SSH and navigate to the "public_html" folder with the command:
cd public_html
Once there run the command and wait for composer to finish installing everything:
composer create-project flarum/flarum
Then navigate to it:
yourdomain.com/public
And follow the steps to configure, as you will be prompted for the data from the database you created earlier. You don't really need to do anything else. The rest are configurations for the type of server you use: Apache, Nginx...etc.
If you want your new forum to show on yourdomain.com instead of yourdomain.com/public follow these steps:
https://docs.flarum.org/install#customizing-paths