Document show up when I start the program

[Geo]

What are templates and how do I change the default template?

Setting Up Templates | SketchUp Help

Selecting a Template
http://help.sketchup.com/en/article/114041

Creating a Template
http://help.sketchup.com/en/article/114916

Automatically loading a template
http://help.sketchup.com/en/article/114911