Update how-to-add-users.md

Author: sdgilley

articles/machine-learning/how-to-add-users.md

@@ -152,7 +152,7 @@ Send the following to your labelers, after filling in your workspace and project
 1. Open [Azure Machine Learning studio](https://ml.azure.com).
 1. Use the dropdown to select the workspace **\<workspace-name\>**.  
 1. Select the **Label data** tool for **\<project-name\>**.
-    :::image type="content" source="media/how-to-add-users/label-data.png" alt-text="Label data tool.":::
+    :::image type="content" source="media/how-to-add-users/label-data.png" alt-text="Screenshot showing the label data tool.":::
 1. For more information about how to label data, see [Labeling images and text documents](how-to-label-data.md).
 
 ## Next steps