Edit Line Height

I’m looking to edit the line height using some sort of custom CSS (I’m assuming) so that the titles don’t overflow on mobile displays. Everything looks fine on a desktop, but when I pull the page up on my iPhone, some of the titles are too long and overflow off of the screen. I don’t see a setting to change this, so I’m assuming that it will take some custom CSS, but I have very little experience with that and no idea where to start. Anybody have any pointers? Thanks in advance!

The page I need help with: [log in to see the link]