Crafting Recipe:

RRR
RMR
RRR

R = Redstone
M = Minecart

Turbos can be crafted like this:

III
III
II

I = Iron Block.

When you enter a car
You will be given a driving stick. Don't lose this as it is required to drive.

Drive by looking in the direction you want to steer and holding w.
Brake by pressing the space bar.
Shift up by left clicking and shift down by right clicking.
That's about it, have fun!