M README.md → README.md

@@ -3,6 +3,21 @@
 here are personal and work-in-progress ports for openbsd. note that they could be
 untested or broken, use on your own risk.
 
+## installation
+
+make sure your port build user is in `wsrc` group.
+
+```
+# umask 002; mkdir /usr/ports-laninpre
+# chgrp wsrc /usr/ports-laninpre
+# echo PORTSDIR_PATH=/usr/ports:/usr/ports/mystuff:/usr/ports-laninpre >> /etc/mk.conf
+# exit
+
+$ git clone https://git.aaoth.xyz/ports.git /usr/ports-laninpre
+$ cd /usr/ports-laninpre
+$ ...
+```
+
 ## contact
 
 `aaoth at aaoth dot xyz`