To resolve a vector we generally consider three points
1.identify the angle that the vector makes with the reference direction . a reference direction may be horizontal , vertical or the X- axis or Y- axis
2. identify the magnitude of the vector . the magnitude of the vector is its size.
3.calculate the components. to calculate the component use formula
magnitude*cos(angle which makes with that direction)
let we calculate x and y component  of a vector whose magnitude is A and make an angle Ф with X-axis.
x component = A*cos(Ф) = AcosФ
y component = A*cos(90-Ф)                (vector make an angle with Y-axis = 90-Ф)
y component = AsinФ