Exclusively pumping

Ma

I decided today to start exclusively pumping. I was told by pediatrician to pump every 2.5 hours and feed every 3 (except at night). She is eating 2-3oz. I just pumped 20 minutes on each and got 5oz. Total. I’m wondering what the best way to store the extra would be? Im currently putting it in another bottle in the fridge and feeding it at room temp. Before giving her the newest bottle. Any advice? I would like to start building a small supply.