It is very easy to increase bitcoin, just by it with your cash.
I think he is referring on how to increase btc by means of working with it not just by buying. if you already have capital, better try how to trade but make sure to educate first yourself on how things work. its not going to be easy and also risky but give it a try. if you became a good trader you will earn for sure.
If you already have capital then try to avoid trading ,try to to invest in legit projects.you can also invest in exchange shares though you will get less profit as its long time investment but a safer one.
If you have capital then you should invest your money in trading. But first you start with a small amount. Try it for atleast 1 or 2 months to gain experience and then you will be ready to increase your bitcoins. But entering trading without getting ready will land you into gambling in the name of trading.