You can use math to compare the position of the thumb from the base of the "analog stick". If they have their thumb within a certain distance from the centre of the circle, get the force to move with from how far they are from centre, and the angle as the angle between the thumb touch and the centre.
I only know Construct Classic at the moment, but I think the commands may be similar.
Condition: If distance(Thumb.X, Thumb.Y, Circle.X, Circle.Y) < CircleRadius
Action: Force = distance(Thumb.X, Thumb.Y, Circle.X, Circle.Y)
Angle = angle(Thumb.X, Thumb.Y, Circle.X, Circle.Y)
(Where Angle and Force are variables, and CircleRadius is Circle.Width / 2)