MTC input devise is usually at the bottom of the Catalyst Control Window
- if not shown, you will need to enable it in catalyst preferences menu / devices tab

Simply select the MIDI device connected to your Mac from the dropdown list (where is says no input)

If you have a more complex MIDI setup - you may have to configure some routing with MacOS MIDI preferences.

MIDI TC is fine - but SMPTE has more configurable options and sync ability within catalyst - so its worth considering if an option.

S