JohnnyEnglish tutorial Working with UE4
If you've never opened Unreal Editor 4 before, I'd recommend doing it now, perhaps follow a few tutorials about using the editor, there are numerous examples, I'll endeavour to add links to good ones here.
For this tutorial I'm going to recommend using the 3rd person shooter template as a way to build and test your map, using the 3rd person shooter template has advantages when testing a map and I'll highlight those as we progress.