You can watch a video on YouTube that shows us how to get started with Power Apps. It is called Getting Started with Power Apps.

At time 8:50, Andrea begins to discuss Power Apps. Power Apps consists of Canvas Apps, Model-Driven Apps, Portals, and the Davaverse. In the video model-driven apps are at time 18:08. Actually, she talks about creating Solutions here. At 28:08 Andrea starts with Portal Apps, however she points out that there is another video for that.

To create a Portal App you need to create an environment for which you need a license. Go to the article Create and manage environments in the Power Platform admin center for more information.