This is meant to be some body text or something I guess. This is really long text and should hopefully wrap at some point. Resize the page to see this in action!
Your main tool here is the flex-direction rule. Set this to row to divide horizontal space; vertical to divide vertical space.
It's worth keeping in mind that flex-box is not just limited to one line as well; you can also use the flex-wrap rule to go to the next row/column.