OBS already starts with one premade scene (Pictured above). You can also create more scenes. Right click the Scenes list box and select Add Scene to do so. (Pictured below)
You can later on change the order of your Scenes, as well as rename delete or duplicate them or set a hotkey.
Now all you need are some sources. After creating your scene, right click the sources list box and select a source to add.
Give it a name and change all necessary settings.
After adding some sources, you may need to Edit the scene