If you want to try PeerTube, the official PeerTube app IS NOT currently a good way to do it. Due to silly app store rules it is missing key features, and there are much better alternatives.
If you just want to watch and interact with PeerTube videos, it's easiest to do it from within Mastodon. For example try visiting @michellemay
If you prefer to use a PeerTube account, use your PeerTube server's website or web app. Here's how to install web apps: https://fedi.tips/how-to-install-web-apps-for-mastodon-and-the-fediverse
Edited 3d ago