My tutorial assumes that you have 3 midi tracks and one audio track. You can do it custom (open a blank project and add tracks according to what you need) or use a template and change it as needed.
You need to insert the TTS synth into the FX bin in the audio track.
You need to be able to import the midi data one way or the other.
You can either use the mouse to draw in the midi notes to tracks 1 thru 3... the midi tracks, or use a live midi keyboard. It's so much easier if you can input the midi from a midi keyboard in real time. This requires a midi input. A midi input becomes available to MC5 when you either connect an interface that supports midi input OR.... if the musical synth keyboard uses USB to communicate with the computer. Your factory sound card generally will not support midi, hence, you don't seem to have a midi input available. As soon as you connect the midi capable device, the midi inputs should appear in your MC5 list for input devices under the MIDI option.
Once you have all that set up, it's simply then a matter of setting up the channel and input/output routing as shown in my tutorial.
Essentially, you record the midi data INTO the midi track. Next, you send the midi data OUT of that track on a channel that corresponds to the same INPUT channel number in TTS. In TTS, that particular channel has a patch assigned to it. Could be piano, bass, strings, flute, bagpipes, drums, or whatever. You can echo that data so that you hear it in real time as you play. You set the details for each track and channel in MC5's Track Inspector window.
It might sound complicated, but once you grasp the concept, it's really very simple.