Circular motion has an acceleration towards the center of the circle. A net force is required towards the center of the circle. This net force is known as centripetal force. To find the net force you must first list all the forces acting on the body.
Possible forces that can be present are weight , tension , friction , reaction , lift force etc.
After resolving forces present , the resultant component along the line joining to the center of the circle is the resultant force (= mv2/r). The component perpendicular to this line has resultant force equal to zero.