Oddly, for a bunch of historical reasons, SmartThings is much better at the complicated than it is at the simple. Which is to say there’s almost always a way to make it do pretty much anything you can think of, but it’s rarely obvious how to get it to do something super simple like just grouping lights to go on and off together. There will probably be three or four different ways to do it, but finding them and getting them set up will feel much more complicated than it seems like it should be. 
In 2016, @ady624 created a new rules engine for SmartThings called core. It took all of those complicated capabilities and wrapped them into one very powerful and sophisticated rules engine. It’s still a lot of work to set up the simple stuff, but at least you’re doing it in one place. And there are many community members who will be glad to help you design and set up your automations.
So at this point, the answer to pretty much any scheduling/rule question is just core. It doesn’t make it feel simple, but it definitely makes it possible.
I’m going to give you a different link than the one that @eric182 gave you just because this one sets up a little more introductory context and gives you a couple of other links that you will probably find helpful as well. So I’m just seconding his suggestion, but with a somewhat easier on-ramp. 