There's no need to wait to utilize the multicurrency feature after upgrading your subscription and activating it, Blaine. I'll show you how to create a new account that uses a foreign currency in the Chart of accounts to keep your financial data organized.

While adding an account, you need to input the Account name and select the Account type first so the Currency drop-down will appear. Please see the attached video below for your reference.

Moreover, it's important to note that once a transaction has been recorded in a multicurrency account, the currency cannot be altered. For more details, refer to this article: Set up and use Multicurrency in QuickBooks Online.

When everything is set up and all associated transactions are assigned to the appropriate currency accounts, you can generate the Realized Exchange Gains & Losses report to get a detailed presentation of your foreign balances and adjustments. 

You can always let me know in the comments if you have any other multicurrency concerns or questions about managing your chart of accounts. We in the Community will get you covered.