With every "original" wire to engine disconnected:

1. Attach a battery cable between the negative post on the battery to a clean/shiny starter attachment bolt (to the clutch housing). You now have a good ground.

2.a. Attach a battery cable between the positive post on the battery to the large post on the foot-starter.

You can now crank the engine by pushing down on the starter button (there is no need to stomp on this button).

or,

2.b.1. If you have a side post on the foot-starter starter-switch (as was originally used in 12v trucks), attach a lead/wire from the side post through a ballast resistor and then to the coil.
or
2.b.2. If you do not have a side post on the foot starter, attach a lead/wire from any 12v source through a ballast resistor and then to the coil.

You can now crank the engine by pushing down on the starter button (there is no need to stomp on this button).

3.note 1: Some might say you can do without the ballast resister for a short running of the engine - I use a ballast resistor.
3.note 2: If you have a resistor coil or an electronic ignition that does not need a ballast resistor, forget about a ballast resistor.

After you run start/run the engine, be sure to disconnect a battery cable.
or
I put a switch in the lead to the coil, this allows you to turn off the engine, without disconnecting a battery cable (be sure to turn that switch on when trying to start the engine).