how do I take an app out of a folder and leave it by itself on the home screen

Open the folder, press and hold the app until they start to wiggle. Then drag it out of the folder to the home screen. Tap Done. Then you can move it to another home screen if desired the same way.

when in the folder.. Tap/hold and select Edit Home Screen like the article you came here from shows...

Then once the apps are jiggling, drag it out of the folder.

Or if you're not sure where the app is.. you can utilize the App Library to help you.

From your Home Screen, swipe left until you get to the App Library.

Swipe downward and you'll get an alphabetical list of your apps.

Locate the app in the list or type the app name into the search field

Once you've located the app, tap/hold then drag it and it'll pop out to your Home Screen

(regardless of where it was located previously)

Organize the Home Screen and App Library on your iPhone - Apple Support