Add notes to self about how to run

README.md

@@ -1,2 +1,12 @@
 # advent-of-code
 Repository to hold Advent of Code (http://adventofcode.com/) solutions.
+
+## Setup
+
+* Set up a virtual environment `python -m venv venv`
+* Activate it `source venv/bin/activate`
+* Install requirements `pip install -r requirements.txt`
+* Set up PYTHONPATH `export PYTHONPATH="${PYTHONPATH}:/path/to/advent-of-code"`
+* Use `python util.py` to set up each day
+* Run each day using `python year_2023/day01/trebuchet.py`
+* Update tox.ini to set default year for testing