When setting up your environment for Single Sign-On across your other web applications (e.g., SharePoint) there are a few local machine settings that needs to be setup on the client side.
Inside the Intranet
Step 1. Navigate to the Internet Explorer (IE) Internet options.
Step 2. Navigate to the Security tab, select Local intranet, and then click on the Sites button.
Step 3. Select Advanced and add the URL domain(s) that are trusted:
Step 4. Finally makes sure that the User Authentication is set to Automatic logon only in Intranet zone.
Step 5. Once configuration is complete, the user will then be able to log into any of the applications once, and would not be prompted the second or ongoing time.
Outside the Intranet
Step 1. Navigate to Control Panel -> User Accounts -> Credential Manager. Click on Add a Windows credential.
Step 2. Enter in the URL address and Username/Password, then click OK.