Solution
The MID Server is a Windows Virtual Machine and you will need to 'RDP(Remote Desktop Protocol)' into the box using a software application such as Microsoft RDP or another of that type.
The username for the mid is always: Administrator and the password is the same as your instance password, it will always be shown on the nowlearning course overview header banner as well as in the email you receive with your lab instance details.
The address to use for the MID is almost the same as the instance but without https:// and with an extra 'mid' suffix in the url, for example:
nowlearning-nlinst0xxxxxx-mid-001.lab.service-now.com
Before connecting to the MID Server, make sure your instance is running because if the instance is hibernating, then the chances are high that the MID is hibernating as well, you can restart both using the 'restart instance' button on your course overview header banner.