Update README

README.md

@@ -68,9 +68,42 @@ authToken, err := client.AuthorizeToken(context.Background(), authKeyPath)
 if err != nil {
 	log.Fatal(err)
 }
-fmt.Println(authToken)
 ```
 
+#### Premium member (Enable to use the [area free](http://radiko.jp/rg/premium/).)
+
+Step 1,2 are the same as above.
+
+```go
+// 3. Create a new Client.
+client, err := radiko.New("")
+if err != nil {
+	panic(err)
+}
+
+// 4. Login as the premium member
+// After client.Login() has succeeded,
+// the client has the valid cookie internally.
+ctx := context.Background()
+login, err := client.Login(ctx, "example@mail.com", "example_password")
+if err != nil {
+    log.Fatal(err)
+}
+if login.StatusCode() != 200 {                       
+    log.Fatalf("Failed to login premium member.\nInvalid status code: %d",
+		login.StatusCode())
+}
+
+// 5. Enables and sets the auth_token.
+// After client.AuthorizeToken() has succeeded,
+// the client has the enabled auth_token internally.
+authToken, err := client.AuthorizeToken(context.Background(), authKeyPath)
+if err != nil {
+	log.Fatal(err)
+}
+```
+
+
 ### ■ Use your authentication token
 
 ```go

login.go

@@ -9,7 +9,7 @@ import (
 	"strings"
 )
 
-// Login returns Statuser that has StatusCode method.
+// Login returns the Statuser that has StatusCode method.
 func (c *Client) Login(ctx context.Context, mail, password string) (Statuser, error) {
 	err := c.login(ctx, mail, password)
 	if err != nil {