Cook couscous in chicken broth according to package instructions. Test a little early. You want the couscous to be al dente. Remove from heat and drain. Leave some of the liquid (broth) in the pan and immediately add onions. Cook onions until translucent, about 5 minutes. Add spinach to pan and toss, lightly, over heat. Add olive oil and toss together. Occasionally toss couscous to cool.