It's very easy for anyone to create a simple mandala using circles and lines. You can use a compass to draw a certain number of concentric circles. Then you divide them with a ruler to even parts, like you would a pizza or a cake. Pick how many (4, 6, 8, 12 or more).
Begin with a first shape and repeat in each little part while rotating the paper.
Continue with one line or shape at a time filling in the rings.
You can always add more circles if you need.
It can be helpful to start with a pencil first and then go in with markers or colors. Experiment with tools and materials and find what feels and works best for you. :)