Add run command to readme

 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 5692a9c..7f879ff 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,7 @@ after that is released)
 - [wlroots](https://github.com/swaywm/wlroots) 0.10.1
 - xkbcommon
 
-Then simply run `zig build`.
+Then simply use `zig build` to build and `zig build run` to run.
 
 River can either be run nested in an X11/wayland session or directly
 from a tty using KMS/DRM.