You can hand express as soon as your baby is born; once you see an increase in the amount of milk expressed, you can use a breast pump.
Pumping and storing breastmilk
When Should I Start Wearing A Breast Pump Bra?
What are the best suction settings to use on a breast pump? - Neb Medical
Increasing Breast Milk Supply - Power Pumping – Pregnancy Birth and Beyond
How to Increase Breast Milk Supply by Pumping
Pumping Guide for Breastfeeding
How Often Should I Pump? A Breast Pumping Guide for New Moms
Bottle Feeding Breast Milk: How to Use Pumped Breast Milk
8 Breast Pumping Techniques to Maximize Milk Output – Pumpables
Increasing Breast Milk Supply - Power Pumping – Pregnancy Birth and Beyond
Why And How To Use A Manual Breast Pump
When can I start using a breast pump?
When to Start Pumping: Too Soon? Too Late?
How much breast milk can I expect to pump in one session? - Milk N Mamas Baby How much breast milk can I expect to pump in one session?