Dixravi
Try going step by step. You alread have SSH access, that's great. The first thing you should do is access your account via SSH. Here is some help regarding this:
https://mediatemple.net/community/products/dv/204403684/connecting-via-ssh-to-your-server
Once you have logged into your account, have a look for Composer. It's a software for dependency management in PHP. It allows you to declare the libraries your project depends on and it will manage (install/update) them for you.
To find out, whether Composer is already installed just type into your console window:
composer
If Composer is installed, you should see something like:
______
/ ____/___ ____ ___ ____ ____ ________ _____
/ / / __ \/ __ `__ \/ __ \/ __ \/ ___/ _ \/ ___/
/ /___/ /_/ / / / / / / /_/ / /_/ (__ ) __/ /
\____/\____/_/ /_/ /_/ .___/\____/____/\___/_/
/_/
Composer version 1.4.2 2017-05-17 08:17:52
Usage:
command [options] [arguments]
Options:
[...]
If Composer is not installed, you will see something like:
-bash: composer: command not found
In this case you have to install it first, you can find instructions about that here.
Once you have installed Composer, installing Flarum is just a command in your SSH console. How to do that is described in the link jordanjay29 gave you.
