updates oauth2 authorization code challenge

apim-lab/7-security/apimanagement-7-3-3-Oauth2-AuthorizationGrantFlow.md

@@ -64,6 +64,24 @@ Every client application that calls the API needs to be registered as an applica
 
 ![client app registration5](../../assets/images/authflow5.png)
 
+### Grant permissions for client-app to call backend-app
+
+- Now we have to open our client app and choose the option `API permissions`
+- In here we need to click on `Add a permission`
+- Then choose `My APIs`
+- Select the record for `backend-app-oauth`
+
+![client app registration5.1](../../assets/images/apimOauthgrants1.png)
+
+- Then select the `Delegated Permissions` option
+- Then mark the `Calculator.Read` checkbox
+- Then click the `Add Permissions` button
+
+![client app registration5.2](../../assets/images/apimOauthgrants2.png)
+
+- Finally click the `Grant admin consent for ...`
+
+![client app registration5.3](../../assets/images/apimOauthgrants3.png)
 
 
 ### Enable OAuth 2.0 in the Developer Console for Authorization Code Grant type