updated readme

README.md

@@ -1,3 +1,9 @@
 # AdventOfCode-2023
 
-Solutions to https://adventofcode.com/2023/
+Solutions to https://adventofcode.com/2023/
+
+In a directory for a specific day,
+
+* To test: `zig build test`;
+* To run (assuming NuShell): `open sample.in | zig build run`;
+* To run (assuming bash): `zig build run < sample.in`.