By default, DAZ Studio 4.6+ Pro will load the Genesis figure when it launches. Studio can be configured to load any scene on startup. You can find the path to this scene in Studio 4 by going to EDIT (Win) / DAZStudio (Mac) --> Preferences --> Startup --> On "Launch" --> Load File. This drop-down can be set to any file which Studio is designed to load and which is located on your computer's hard drive. It can also be set to 'none' if you do not wish any file or scene to launch on startup.
If you get a message about a Genesis.dsf or Genesis.duf file not being found when you launch Studio, check the path to make sure it is valid. Also, make sure you have actually installed Genesis Starter Essentials. Genesis.dsf is the old format for Genesis. Studio can still read it, but Genesis is provided as a .duf file. If your Studio is looking for Genesis.dsf, but you have the newer Genesis.duf, then it will not find it for the default scene. You can change the path.
By default the Genesis.duf file will be here:
/Users/Shared/My DAZ 3D Library/People/Genesis/Genesis.duf
C:\Users\Public\Documents\My DAZ 3D Library\People\Genesis\Genesis.duf
You can change the path in Studio to match the correct location of Genesis.duf on your hard drive.