docs: add instructions

Author: jamesgeorge007

README.md

@@ -5,3 +5,39 @@ Updates `README.md` with the recent GitHub activity of a user.
 <img width="735" alt="profile-repo" src="https://user-images.githubusercontent.com/25279263/87703301-3aa4a500-c7b8-11ea-8eb6-245121997a7b.png">
 
 ---
+
+## Instructions
+
+- Add the comment `<!--START_SECTION:activity-->` (entry point) within `README.md`. You can find an example [here](https://github.com/jamesgeorge007/jamesgeorge007/blob/master/README.md).
+
+- Create a [personal access token](https://docs.github.com/en/github/authenticating-to-github/creating-a-personal-access-token) with `repo` scope and store it as a [secret](https://docs.github.com/en/actions/configuring-and-managing-workflows/creating-and-storing-encrypted-secrets) from the repo settings.
+
+- It's the time to create a workflow file.
+
+`.github/workflows/update-readme.yml`
+
+```yml
+name: Update README
+
+on:
+  schedule:
+    - cron: '*/30 * * * *'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: jamesgeorge007/github-activity-readme@master
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_PAT: ${{ secrets.GH_PAT }}
+          GH_USERNAME: <username>
+```
+
+The above job runs every half an hour, you can change it as you wish based on the [cron syntax](https://jasonet.co/posts/scheduled-actions/#the-cron-syntax).
+
+You can find an example [here](https://github.com/jamesgeorge007/jamesgeorge007/blob/master/.github/workflows/update-readme.yml).
+
+_Inspired by [JasonEtco/activity-box](https://github.com/JasonEtco/activity-box)_