update readme.md

Author: jiachengxu

README.md

@@ -1,3 +1,34 @@
 # raindrop-sdk-go
 
 Unofficial [Raindrop.io](https://raindrop.io/) Go SDK.
+
+## Create an Access Token
+Follow the [offiical raindrop.io authentication documentation](https://developer.raindrop.io/v1/authentication/token) to create an access token, which will be used by the SDK.
+
+## Installation
+```
+go get github.com/jiachengxu/raindrop-sdk-go@v0.1.0
+```
+## Examples
+```golang
+package main
+
+import (
+	"fmt"
+
+	"github.com/jiachengxu/raindrop-sdk-go"
+)
+
+func main() {
+	client := raindrop.NewClient("your_test_token_here")
+
+	// Example: Get collections
+	collections, err := client.GetRootCollections()
+	if err != nil {
+		fmt.Println("Error fetching collections:", err)
+		return
+	}
+
+	fmt.Println(collections)
+}
+```