Express as often as you can, you can add each oz together as long as they were expressed in the same 24h and then freeze them. Morning is when you have highest milk. EBM lasts 6-8 hours at room temp, 5 days in the back of the fridge (not near the door) and up to 6 months in the freezer. If you defrost in the fridge you have 24 hours to use. Or you can defrost in warm water (not hot) and use immediately.
How old is LO? Have you given a bottle before at all? Xx