What error message do you get when you try to add an engine?
As tcochran said above, you should connect your z500 to the fixed1 input of the TIU. That will power the TIU and send power to any tracks connected to the fixed1 output.
Put one engine on the track then turn on the power and try to add it to the remote. Let us know what error message you get when you try this to help narrow down the possible problems.