Unity and source control (sourcetree)

I have an online repositery and I’m using sourcetree. I don’t understand how do I commit my codes, I have a lot of files and I want to commit only one folder. What do I do?

That’s a question about sourcetree, not unity. Have you tried asking in another forum?

True, this is a question for the Atlassian Community, but also already answered in their documentation: SourceTree - Getting Started

The only thing to know before reading, is: Do you use Mercurial or Git? Then just read through the getting started tutorials, they explain everything in detail.