Account sharing is an Accountit Plus feature, please make sure that you have purchased Accountit Plus first, you will then have multiple ways to share an account with another iCloud user that you can find below:

1. By swiping on the account row in the list from left to right and then tapping on the 'Share' button.
2. By long-pressing the account in the list and then selecting the 'Share' option from the menu.
3. By tapping on the 'Settings' button in the top right corner of any account’s transactions list and then tapping on the 'Share' button on iOS or by simply tapping on the 'Share' button in the account's transactions list’s toolbar on iPadOS.