Download app, throw in a small amount of money, $30 or $50 or whatever, buy some bitcoin, and when the price goes up which it will sell for a profit. Or hold on to it for as long as you're comfortable.
I want no part of bitcoin because it's an environmental menace but it isn't any more complicated than what I described.
http://money.cnn.com/2017/12/07/technology/bitcoin-energy-environment/index.html