How to add the proxy to Telegram
After payment, My proxies shows a link that starts with tg://proxy. Open it on a phone or computer with Telegram installed and the app asks whether to connect through the proxy. You can also add it by hand in Telegram's proxy settings, choosing MTProto and entering the server, port and secret from the link.
What an MTProto proxy does and does not do
It carries Telegram traffic only. Browsers and other apps are not affected and cannot use it. If you need a proxy for websites or other software, choose a datacenter, ISP or residential proxy instead.