The help file instructions have the format backwards.
From the help:
The import file format is identifier; display name
It should read something like this:
The import file format is display name, identifier. The column header is not required.
Computer1,<MacAddress of computer 1>
Computer2,<MacAddres of computer 2>
Thanks Joe for your help.
Please note that the spaces after the comma are very important. If you don't place spaces after the comma, the data will not be imported.