If you can tune it you can string it. The strings are cheap. For acoustic I recommend Martins – the blue pack, custom light. Electric: Ernie Ball Regular Slinky - green pack.

Pick up a string winder/wire cutter combo. I use the one I bought 27 years ago. The tool might include something to take the bridge pins off but you’re better off wrapping the bridge pin in an old T-shirt and using pliers – detune the guitar first, alternating strings. Heaviest string, lightest string, 2nd heaviest, 2nd lightest… You’ll put the strings on in the same order.

You’ll need lemon oil or mineral oil. Put a dab on a rag and rub down the fretboard after you take the old strings off. That’ll both hydrate the fretboard and clean it at the same time. This is also when I dust the head and body near the bridge where it’s hard to clean with the strings on.

The first time is a little tricky but after that it’s all muscle memory. After it’s stringed and tuned it’ll probably fall out of tune for the first week or so. That’s the strings stretching and it’s completely normal.

As for a tuner I just use a phone app. It’s accurate enough for my use. If it’s a budget acoustic you should consider upgrading the bridge pins to either bone or brass, $10. They’ll sound better and are more durable. If it’s an electric, ignore everything I said about bridge pins. It’s either strung through the body or the bridge. You won’t have them.

Sorry for the wall-o-text.