Burning an ISO file is a little different than burning ordinary files or music. If you've never burned an ISO file to a disc before, I recommend following the instructions I linked to in the last sentence. It's not a difficult process but there are very important things that you need to be aware of.
Note: If the ISO file is not burned properly, PC Login Now won't work.
After burning the PC Login Now ISO file to disc, go to the computer that you're trying to gain access to and continue to the next step.