Sketchup free for Mac book air

Hi, I am wanting to use sketchup free for Macbook air and signed onto Trimble etc.
I’ve opened up sketchup in a browser.
I can’t find how to start. A white screen with the cube sketchup logo is in the middle of the screen and I don’t seem to be able to open anything or start in general,

First time user, please help anyone, would be much appreciated.

Matt

Perhaps try using a different browser, Chrome, for instance.