Qn for breastfeeding mums

Hi mamas! Need some advice from breastfeeding mums. I'll be bringing my baby out for the first time. He's usually latching but we've tried bottle feeding him on and off. When you bring baby out but you prefer to bottle feed baby, how do you prepare the milk? How do I keep milk thawed, how do I melt it and then warm it up when I'm outside? Or is it just easier to find a nursing room to breastfeed? #firstmom