When you are doing day trading one of your firsts concerns is how much to trade. If this is your first trading experience, you will learn that it is a smart move to have a diversified portfolio; do not put all your eggs in the same nest. Also, do not bet all in one trade; trading is a bet with all the technical analysis behind to reduce the loss risk, but at the end of the day it is still a bet.
With all that said, you will need to define a percentage per bet. For example, I like to bet 2% of my capital per trade. I will talk about how to know how much money that 2% means.