Why do you think acetic anhydride is the limiting reagent? There are more moles of acetic anhydride than moles of salicylic acid.
Anyway, to figure out the theoretical yield, you use the stoichiometric coefficients from your balanced chemical reaction. From the balanced chemical reaction, you know that one mole of salicylic acid reacts to produce one mole of aspirin. So, if you react 0.0158 moles of salicylic acid, how many moles of aspirin would you expect to produce? What mass of aspirin would this amount of moles equate to?