update readme

README.md

@@ -3,3 +3,12 @@
 Scala wrapper for [MoultingYAML](https://github.com/jcazevedo/moultingyaml) and [Play JSON](https://github.com/playframework/play-json),
 in order to convert from yaml to json, and vice versa.
 
+## How to use
+
+When you use it in Scala, add some words as below.
+
+```build.sbt
+lazy val yourProject = Project(...
+
+  ).dependsOn(ProjectRef(uri("git://github.com/nyango/format-converter.git"), "root"))
+```