Take a first aid + CPR class. You can get them that cover everything in as little as 4 hours, but try to get a longer one since they go more in depth. They cover most of the common situations and so will make you calmer when it happens because you had a couple drills. Even if you don't remember the details you will remember something - and when you call the emergency number it will come back what you are supposed to do making it easier for them to explain it.

Everybody should take first aid and CPR classes every few years. Ideally keep your certification up to date, but even if you certification is 20 years out of date, when you need it you will have a clue and so be a lot more helpful.