The begin with the engine.

If you begin with an empty template, you see only this:


This is the project. But you cannot yet place scenes, etc. First, the project needs a viewport.

Go to the Edit menu and choose 'Add User Interface'. There are many choices. You can add, for example, an UI control. But you need a viewport. Look on the bottom of the menu. You see two viewports, a 2D and a 3D. You can also click with the mouse the rightbutton on the Group1 name. Go to the same menu and you can choose a viewport.

Here, you see a 2D viewport.