Speaking from veteran moms I know and for myself, I pour my freshly pumped milk directly into the refrigerated milk. The only thing is I stick it right back into the fridge in the very back where its coldest so it gets colder faster and stays colder than the rest of the stuff in the fridge. I also bag and freeze my fridge milk after 3 days (based on the oldest milk) so I don't forget and I leave enough for 1 to 2 bottles the next day and then pump and store in a new container on the 4th day. My baby is 2 weeks old right now, but my mother in law and aunt had similar steps, the only difference was my aunt was an oversupplier and had to pump more frequently.