If you are looking to create a new Power pages then you are at the right place.
First thing, you need to go to following URL to get started (make sure you have admin rights in D365)
You will see a screen like below, make sure you select correct environment
You can either start a portal from blank or you can select a template (there are plenty of templates which you can choose from).
In our case, we will selecta template (Start with template)
On next screen, we need to select a template. For now, we will go with Starter layout 1