I cannot find the place that I can start a project?
There are multiple ways to do it.
On the Recents page, you can click either on the + button on the top right, or the blue button on the middle buttom:
On the Designs page, you can use the + same as on Recents, or the blue button in the middle:
You can also import an existing model using the import button next to the + one, or double clicking on an associated file in Finder.