Update README.md

Author: arielm

README.md

@@ -1,2 +1,28 @@
 # code
-Source code for some of the examples featured in my blog
+
+Source code for some of the examples featured in my [blog](https://arielm.github.io/cross-blog).
+
+### Instructions
+
+1. Following [these instructions](https://arielm.github.io/cross-blog/2022/10/06/hello-world.html) for running on macOS or Linux, or [these instructions](https://arielm.github.io/cross-blog/2022/10/06/running-in-the-browser.html) for running in the browser.
+
+2. Clone this repository with:
+   ```
+   git clone https://github.com/arielm/code
+   ```
+
+3. Add `CODE_PATH` variable:
+   ```
+   export CODE_PATH=path/to/code
+   ```
+
+4. Pick a sketch, e.g.
+   ```
+   cd $CODE_PATH/sketches/Drawing2dText
+   ```
+
+5. Run for your platform of choice:
+   ```
+   RUN_TEST -DPLATFORM=???
+   ```
+   Supported platform identifiers: `osx`, `linux`, `emscripten`