The perimeter of a polygon or any shape is just the sum of all of its sides. If you are asked to find the perimeter of a polygon, you would simply just add all the sides together. For example, if a square has 4 sides with the length 2m, the perimeter of that square would be 2m + 2m + 2m + 2m = 8m. Perimeter just means add all the sides.
