...
Click on 'Test' to see if the credentials you have used are OK for this purpose and if they are, click Save. Then, in the same page, click 'Synchronize' to get all and you should be ready.
Troubleshooting:
If the above take place and the system still fails to connect, or if the integration initially succeeds but later with the same settings it fails-users failing to login, please make sure that an actual IP is used and not host name in the 'HostName' field.