>>8676702I'd recommend running a classic Tama first. They tend to sell for pretty cheap on eBay and give a very solid overview of the general Tamagotchi experience. The licensed Nanos are nice, but aren't the full experience. Also, you should choose one with a theme you really like.
Gameplay is this: after you set the clock, a baby Tamagotchi will be born. Use the left button (A) to navigate options, the middle button (B) to select an option, and the right button (C) to cancel. If no option is selected, B will show the clock screen.
On the classic Tamagotchi and most versions since, there are four stages of life: baby, child, teen, and adult, and sometimes a secret stage if you know what to do. The baby stage is the shortest (65 minutes) but also it needs the most care. It gets a little easier to care for once it becomes a child. They go to sleep at night, so you don't have to worry about it dying in the middle of the night. How well you care for it throughout its youth determines which adult you get, and how long it lives. Once it dies, you can see what age it died and then start again with a new egg.
Nanos are a little different. They're not terribly needy, and tend to only have two growth stages. The baby often evolves 24 hours after it's born, and then you try to see how long you can keep it alive. In general, you can get the pretty healthy adults from the bare minimum interaction. So if you're a busy person and don't have time to get really invested, they're probably a good option.