Update README.md

Author: alexcheng1982

README.md

@@ -8,4 +8,38 @@ The motivation of this `ChatModel` implementation is to use Spring AI with Sprin
 Supported features:
 
 - Chat completions
-- Function calling
+- Function calling
+
+## Use ChatModel
+
+Add Maven dependency.
+
+```xml
+
+<dependency>
+  <groupId>com.javaaidev</groupId>
+  <artifactId>openai-chatmodel-standalone</artifactId>
+  <version>0.2.0</version>
+</dependency>
+```
+
+To use this `ChatModel`,
+
+1. Create an `OpenAIClient`
+2. Create an `OpenAIChatModel`
+3. Create a Spring AI `ChatClient.Builder` with this `ChatModel`
+4. Create a Spring AI `ChatClient` from `ChatClient.Builder`
+
+See the code below:
+
+```kotlin
+val client = OpenAIOkHttpClient.fromEnv()
+val chatModel = OpenAIChatModel(client)
+val chatOptions = OpenAiChatOptions.builder()
+    .model("gpt-3.5-turbo")
+    .build()
+val chatClient =
+    ChatClient.builder(chatModel).defaultOptions(chatOptions).build()
+val response = chatClient.prompt().user("tell me a joke")
+    .call().content()
+```