Welcome! 
As you’ve noticed, SmartThings is very powerful, but not very intuitive. But you can always ask questions in the forums and people will be glad to help.
@jkp has given you good advice on the locks.
On a more general level, here are two good resources for newcomers.
First, this describes the various options for controlling your devices ( this is a clickable link):
Next, if you look in the community – created wiki at the quick browse lists in the project report section and look at the list for “get started” you’ll find lots of topics of interest to new people. Everything from “the top 10 things to do with SmartThings” to an “impress your friends” List. Lots of topics, both practical and just for fun stuff.
The quick browse lists are always a good place to start, but again if you can’t find what you’re looking for, there will always be forum members who are glad to help.
(Because this is an international forum and the device selection does vary from region to region, just make sure you specify what country you’re in when you ask specific questions.)