If you are looping, you want one continuous loop of pipe all the way around the pool. The water coming from the pump and going to each of the returns branches off of the loop with a T connector. Ideally the lines going from the loop to each of the returns should be relatively short and all the same length. The loop pipe must also be relatively large compared to the final diameter of the return eyeballs.
Looping is not the only way to balance the returns, nor does it work perfectly in every possible situation. Still, it is a simple solution that is easy to use when there are many returns without requiring any calculations.