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.
He told that by just buying coins he cna help to increase the price of bitcoin i think this is kot the only way to increase if you really want to increase to need to be a big part of it trading can be the way to increase the pirce the volume and the demand of one coin not because you had it doesn't mean you make it tho.
i think it is not possible to increase or decrease the price of bitcoin. it need very big investment, in past it was just possible because at that time the volume was not too much. but now the number of bitcoin investors are increase too much and are increasing continuously, therefore it is now becoming more and more difficult to manipulate the price of bitcoin.