To enable the "Alternate Authentication Credentials" in the VSTS account:
1. When logged into the VSTS account using the webpage.
2. In the upper right-hand corner, click on your account button and select “Security” from the drop-down list.
3. On the left-hand side menu, select “Alternate authentication credentials”
4. Check the “Enable alternate authentication credentials” and enter a username and password for logging into VSTS using an external application.