What kind of phone?
Apple? Launch the “App Store” app on your phone, click the “search” magnifying glass, touch the space it shows you next to the pic of a magnifying glass and type Telegram into it. “Get” the Telegram App.
(You can type Truth Social to get the Truth Social app for IOS, as well.)
Android?
Same steps, except you start with the “Play Store”. (No Truth Social app there yet.)
Samsung android.