add installation instructions

README.md

@@ -4,7 +4,19 @@ Gradle utility written in Rust.
 
 Note that this project is still at the alpha stage. The functionalities and behaviors may change.
 
-## Subcommands
+## Install
+
+You can find the pre-built binaries at the [release page](https://github.com/jason5lee/gradle-util-rs/releases). You can build and install it via `cargo install gradle-util-rs --version 0.1.0-alpha.1`.
+
+## Usage
+
+```
+USAGE:
+    gur <SUBCOMMAND>
+
+SUBCOMMANDS:
+    set-new    Watch for the new Gradle project and set the gradle version
+```
 
 ### `set-new`