How do I sign into my iMovie account to see what my balance is or if I have a payment due or what plan I have?

You can also access your accounts from the individual websites for which you have an account, as for example, iTunes. There will be an account item in the main menu of the website. However, since iMovie is free there is no account, other than to show it as a purchase on the app store Account/purchases page.

-- Rich

Your Apple account is your Apple I.D. that you can use to sign in with your password. iMovie is free so there will be no balance, or payment due, or any plan. If you have subscriptions, like Apple Music, possibly there will be an account status item for it. Not sure.

In any event, you can sign into your account with your Apple I.D. and password. See this link for instructions:

Sign in with your Apple ID - Apple Support

-- Rich