This is a difficult question since it is so broad, but I’ll take a swing. If you are in an org that is currently using a traditional waterfall-ish way of developing software, you might start by forming a small team, maybe 4 or 5 people, developer(s), tester, product person. The team should have all the skills they need to develop software.
When you have that team, start giving them small pieces of software that they can build, test, and deliver in a week or two. Focus on the value and deliver something your customer can use each one or two weeks.
The ideas are very simple, the practice is very complex.
I’d also recommend reading Ron Jeffries new book, The Nature of Software Development.