Telegram is available in a variety of web, desktop and mobile apps. Find the ones you want to use here:
Install on the device(s) you want and then enter your country code and phone number. Note, if you are installing on device other than your phone you will need to confirm on your phone.
The Settings tab provides some sophisticated control over notifications and sounds, privacy and security, chat settings and background.
In Settings you can also set up a public username on Telegram if you want to. Note: that if you do, other people will be able to find you by this username and contact you without knowing your phone number, as your username will appear in contacts search. This way people who find you will be able to send you messages, even if they don’t know your number. If you are not comfortable with this, don’t set up a username in Telegram. If you do set up a username and then want to delete it, then you can simply overwrite it in Settings with a blank username.