How to use the turboprop engine?

[MAFman]

How do you use the turboprop engine for single-engine planes? When I’ve tried, it makes the plane roll in the opposite direction because of the torque, and it doesn’t get the plane going fast enough to take off.

[OHara]

It is not easy (probably intentionally).  From what you say, I think you want to put the propeller at a more 'flat' angle, about 10° from having the blades in the plane of the propeller's disk.  Then the blades cut through the air with less drag.  I've borrowed an image from someone's plane posted to KerbalX that shows a reasonable blade-angle for takeoff.

KerbalX is a good place to find examples, if you want.  (Beware that searching the word 'turboprop' will find examples form before KSP had the turboprop part, where players build their own turbine engines from smaller parts.)

There is still a tendency to roll, which you can balance with trim (alt-E and a little alt-D on PC) as one does on real single-engine aircraft.

Once you are airborne, you can increase the angle of the blades to get more speed.  This part of the game encourages a lot of experimentation and adjusting of the craft. 

[Gargamel]

Moved to Gameplay Questions.

[Echo__3]

So, making prop planes is a little different than making jets. You will need to make sure the blades are deployed. You need a blade angle around 9 degrees to get moving when stationary. The faster the plane goes, the more you will need to angle the blades. There are different ways to do this, but I like to use the KAL-1000 to set the blade deployment angle from 0 to 45 degrees. You can bind this to either one of the translation controls or to the main throttle. Here are a couple of tutorials that may help you.