When an object is placed on the inclined plane, its weight is resolved into normal force. This force is equal to perpendicular to plane.
Normal force equals to Fcosθ
N =W = Fcosθ
Normal force can be calculated by finding the weight of the object.
Weight = mg
Where m is mass of object
g is acceleration due to gravity
N = mgcosθ
This is the magnitude of normal force.