I'm thinking you mean you're not sure what's going on because you see three separate circuits that are not physically connected to one another.
With these type of schematics, you're supposed to follow the input and output of each component or individually drawn circuit, and then find the similar label on the other circuits to make the physical connection.
On complex schematics, sometimes those connection component labels may not even be on the same page of a large circuit.
It's not unusual for somebody to show the 5V voltage regulator (the red box in the lower right) by itself, with it's input and outputs labeled.
You're supposed to know that the Pin 3 (VO or Voltage Out) is supposed to be connected to the J2 (Pin 2) connector in the upper left of the drawing, just by looking for its location.
It's just a personal opinion, but I think this type of drawing is just laziness by whomever did it. I guess that he has 'cells' made-up of graphics, and just uses each individual graphic picture-cell which he has previously made in his
computer memory, and displays them with the labels of inputs and outputs that you're supposed to locate. It works well for the person doing this, because he can re-use the graphic cells in several different circuits this way,
instead of generating a one-time only complete circuit for each complete circuit that he produces.
You might have to ask the guy who made the drawing, but the explanation in the text seems to indicate he wants you to connect J1 & J2 together, to complete that part of this circuit.
That's a bit unusual, because most schematics I've seen just label J1 on one part of the circuit, and then you look for the same J1 label input on another part of the drawing that shows the point where the connection of the
then J2 connector more-complete full circuit is at.
So, Your voltage regulator input is the 8.4/12V input at Pin 1 (with the negative side of the power supply to ground)
The 5V out from voltage regulator Pin 3, goes to connector J2 Pin2 in the upper left part of the drawing.
All grounds in the circuit are supposed to be connected to the same 8..4V/12V negative (ground) common connection point.
Like I said, I think the originator wants you to connect J1 & J2 together to make that physical connection between those two parts of this circuit.
The M1 and M2 are supposed to be Motor Connections.
Oh, the S1 is just an on/off switch from the input power supply, to Pin 2 of your 5V voltage regulator.
Is this any help, or as Martaine2005 asked, are we talking about what you're asking, or are we missing the point of your question?
