There are two solutions.
1. Specify "destination" as value of property "Credential Type". And add new entry in Agentless Remote Connections in Administration Tab as below. In this case, you don't need to specify username/password in property of plugin
2. Specify "property" as value of property "Credential Type" and specify username/password.
And if HAD can't conect remote server, please check followings.
1. Does the user belongs to Administrator Group? User need to belongs to Administrator Group
2. Please check need or not to specify domain name like domain\username
3. Is the target host Windows? If yes, did registry settings done on target host (Windows)? Please see "Preconditions for an agentless connection place (Windows)" section in HAD Installation guide.