I have installed this App in to my IPhone and IPad, but I can’t find the App in my IMac

A warm welcome to the Community, info-supsweeper-.

Once you've installed the app, you can launch and open it through the Finder folder. Here's how:

1. Select the Finder icon on the bottom left corner of your mac.
2. Choose the Applications folder, then open QuickBooks.
3. You should see the message, QuickBooks wants to use your confidential information stored in Intuit ID... in your keychain. This is simply macOS validating the new application.
4. To avoid seeing the message again, enter your login password, then select Always allow.

To get more details about the QuickBooks mobile app, see the resources below:

QuickBooks Online app overview.

QuickBooks Online Mobile app FAQ.

If I can be of additional assistance while working with the QuickBooks app, don't hesitate to let me know. I'd be more than willing to lend you a hand.