update README.md

Author: smasato

README.md

@@ -2,12 +2,31 @@
 
 An experimental type-level Ruby interpreter for testing and understanding Ruby code.
 
+## Installation
+
+Install via RubyGems.
+
+```sh
+$ gem install typeprof
+```
+
+### Requirements
+
+TypeProf supports Ruby 3.3 or later.
+
+## Quick start
+
+1. Install VSCode [Ruby TypeProf](https://marketplace.visualstudio.com/items?itemName=mame.ruby-typeprof) extension: `code --install-extension mame.ruby-typeprof`
+2. Run `typeprof --init` in your project root to create `typeprof.config.jsonc` file.
+    Other options are available. See [typeprof.conf.jsonc](typeprof.conf.jsonc) for details.
+
+3. Reopen your project in VSCode.
+
 ## Development
 
-1. Install Ruby 3.3 or later.
-2. Git clone this repository: `git clone https://github.com/ruby/typeprof.git`
-3. Install VSCode extension: `code --install-extension mame.ruby-typeprof`
-4. Open the repository in VSCode: `code typeprof`
+1. Git clone this repository: `git clone https://github.com/ruby/typeprof.git`
+2. Install VSCode [Ruby TypeProf](https://marketplace.visualstudio.com/items?itemName=mame.ruby-typeprof) extension: `code --install-extension mame.ruby-typeprof`
+3. Open the repository in VSCode: `code typeprof`
 
 ### Testing