Your ChatId is the long number which identifies you on telegram. Each user has one & so does each group chat (although those are negative numbers). You'll want to know what yours is so that we can limit access to our bot's commands depending on who is issuing them.

There are many ways of getting your ChatID, but we're going to limit this to two. The first (& easiest if you're happy using someone else's bot to do the work) is to start a telegram chat with @get_id_bot

The second involves us adding our first command to the telegram bot that we are writing. Follow the link if you haven't got a command node & telegram bot config set up already...

To get our chatId we will need to chat to our bot & to get it to respond to a command with the information that we need. The command node was set up in the instructions about getting started (/getID), so we need to add a response.

From the palette (on the left hand side) drag a change node & a telegram sender node onto the flow. Then connect the output of the command node to the change node & the change node to the sender node.
Configure the sender node like this, then set the sender node to use the telegrambot config that we created when we set up the command (we'll be using the same one for everything from here in). Note the J: in that bottom box, it's important.

There we have it, our first NodeRed flow & our first telgram bot command.

If you start a chat with your bot & send the message "/GetID" then you should get your ChatID back as a message from your bot.