Add usage part in README

README.md

@@ -1,2 +1,14 @@
 # moleculec-es
 ECMAScript plugin for the molecule serialization system
+
+# Usage
+
+First, download precompiled binary from [releases](https://github.com/xxuejie/moleculec-es/releases) page, and put the binary in our PATH. You could also clone and build the project from source. The only dependency is Golang here.
+
+```
+$ cargo install moleculec
+$ moleculec --language - --schema-file "your schema file" --format json > /tmp/schema.json
+$ moleculec-es -inputFile /tmp/schema.json -outputFile "your JS file"
+```
+
+Generated file from this project follows latest ECMAScript standard, it is also orgnaized as an ECMAScript module to allow for tree shaking.