readme: usage

Author: uggedal

README.md

@@ -10,4 +10,17 @@ Requirements
 * xbps
 * git
 
+Usage
+-----
+
+1. Create a dedicated user for `void-updates` which is member of the
+   `xbuilder` group.
+2. Run a command like the following from the dedicated user's crontab
+   daily:
+
+    void-updates -p 20 \
+      -r git://github.com/voidlinux/void-packages.git \
+      -s /var/cache/void-packages \
+      -o /srv/http/void-updates
+
 [void-packages]: https://github.com/voidlinux/void-packages