Bit of confusion here - NCM will use whatever connection profile you set to download configs, config change templates, etc. In the case of the screen shot above, that would be telnet. (I would prefer to use SSH, but that is the same area)
So, if you are getting connection refused - first make sure you can telnet / ssh into the device from your NCM server (or additional pollers, if you have the feature enabled)
If you cannot, then either you have invalid username/password or your blocked by ACLs.
Once you can successfully telnet /ssh in manually - set that same configuration up in the connections profile dialog box.