Add setup instructions to readme

README.md

@@ -2,6 +2,54 @@
 
 Keeping an eye on the Hack Club Slack’s [#counttoamillion](https://hackclub.slack.com/archives/CDJMS683D) channel.
 
+## Setup
+
+### Creating the Slack app
+
+You’ll need to create a Slack app (not a classic one) with at least the following bot token scopes. The reasons each scope is required are also included:
+
+- `channels:history` (or `groups:history`, if it’s a private channel): Used to listen to messages sent.
+- `chat:write`: Used for sending messages.
+- `reactions:write`: For reacting to invalid messages.
+
+Then you’ll need to subscribe the app to a few events. The server has an endpoint open at `/slack/events`, so when you’re asked for a request URL, just put `https://<SERVER>/slack/events`. Only the following events are needed:
+
+- `message.channels` (or `message.groups` if it’s a private channel)
+
+### Environment variables
+
+Here are all the variables you need to set up, with hints.
+
+```bash
+# The port to run the app server on
+PORT=3000
+# Redis database to store the last number and its sender
+REDIS_URL=redis://…
+# App config. Obtained from the "Basic Information" page of your app.
+SLACK_CLIENT_BOT_TOKEN=xoxb-…
+SLACK_VERIFICATION_TOKEN=xxxx…
+# The channel where Jia should validate counted numbers in.
+SLACK_CHANNEL_ID=C…
+```
+
+### Deploying
+
+```bash
+# Run it…
+make
+
+# …or build a binary and run that instead
+make build
+./bin/jia
+```
+
+After you’ve followed all the above steps, you should see something like this:
+
+```bash
+Starting Jia…
+Listening on port 3000
+```
+
 ## License
 
 [MIT License](LICENSE.txt)