You need a copy of the Foundry stack on any page where you use Foundry stacks. It has the base settings for lots of things like paragraph and header fonts, colors, etc. The control center stack is the one named “Foundry”.
You should probably start with the Quickstart area of the Foundry documentation.
https://foundry.elixirgraphics.com/documentation/quickstart/
If you are not familiar with the Partials feature of Stacks, you should also learn about them before you start making mutiple pages. They allow you to have the same stack on multiple pages that all use the same settings. They are good for things like: the main Foundry stack, your navigation, your footer, etc. Basically, things you want to always be the same on your pages should be in a partial.
Info on Partials can be found here. Partials work the same in v4 as in v3: