How (or which) topical perscription do I use for my acne

Patient: Hi I have moderate acne and was prescribed Doxine 100 (Doxycycline) antibiotic and my doctor also prescribed me two topical treatments; Differin Gel (0.1%) and ReTrieve Cream. both of these are to be used at night so I was a little confused as to whether im supposed to use both of these or just one of them? Im really just not sure how im supposed to use them, do I alternate them nightly? Do I use both on same night? if so in what order? or do I just pick one of them to try it? I was just a little thrown back that I had prescriptions for two topical treatments that are both to be applied at night? Thanks in advance!

Doctor: