It works; add an appropriate README.

README.md

@@ -1 +1,21 @@
-# 2020-07-13-pyhep2020-tutorial
+## Uproot and Awkward Arrays
+
+Tutorial PyHEP 2020, presented on July 13, 2020 at 15:10 CET, 06:10 PDT, 18:40 IST, 22:10 JST by [Jim Pivarski](mailto:pivarski@princeton.edu) (Princeton University).
+
+See [the agenda](https://indico.cern.ch/event/882824/timetable).
+
+## How to participate
+
+The preferred way to participate is to run the JupyterLab code with me, evaluating the code as we go and trying your own modifications.
+
+You can run it on a public cloud service called Binder:
+
+<br>
+<p align="center">
+  <a href="https://mybinder.org/v2/gh/jpivarski/2020-07-13-pyhep2020-tutorial.git/1.0?urlpath=lab/tree/tutorial.ipynb">
+    <img src="https://mybinder.org/badge_logo.svg" alt="Launch Binder" height="40">
+  </a>
+</p>
+<br>
+
+If you instead want to run everything on your own laptop, use pip to install the packages listed in [requirements.txt](requirements.txt) and open [tutorial.ipynb](tutorial.ipynb) in Jupyter.