Go to the start page (also known as Speed Dial). At the left side is a navigation bar, it should have icons on it for Facebook, Whatsapp and Telegram (though you can hide any you aren't interested in), and an icon at the bottom of the navigation bar changes it to a sidebar so that it is always visible. Of course you'll need to login to whichever messenger(s) you use, but that should be it.
Sorry sgunhouse but there's no Telegram on that side bar, only Messenger and Whatsapp. There's no other way to enable Telegram messaging?