You can change your bot's information (description, name and so on) only through @BotFather.
How to change your bot's information:
1. Open the @BotFather bot.
2. Send the /mybots command to @BotFather and tap the username of the bot you need on the keyboard below the message.
3. Tap "Edit Bot" on the keyboard below the message.
4. Tap "Edit About" on the keyboard below the message.
5. Send the text you want to see.
Congratulations! Your bot's information has been changed.
Important! If the name hasn't changed, wait a few minutes or restart your Telegram client.