First, it depends what shape it is.
To find the area of the:
square/rectangle: L x W (length times width)\
Triangle: 1/2 x b x h (One half times base times height)
Parallelogram: b x h (base times height)
Circle:
x r^2 (Pi times radius to the power of 2)
Trapezoid: 1/2 x (a+b) x h (One-half times Base 1 plus Base two times height
Disclaimer: These are the areas for MOST shapes, not all.
hope this helpeed :)