I assume you have installer already on your iPhone?
Run it, make sure to install ‘Community Resources’.
After this, go back to installer and you should see OpenSSH.
Install that and SSH will be enabled on your iPhone.
However, if you only want to install cool apps on the iPhone, there is no need for SSH, simply go to installer, install "Community Services" and then when you go to installer again, all the cool apps will be there for you to install.
Just a tip - if you do install SSH, make sure to install iToggle (from installer) to turn SSH off when you are not using it as it drains battery life substantially