Follow the steps below to enable multiple currencies or add additional currencies on QuickBooks Online.
1. Click the setting icon on the top right of the QuickBooks Online dashboard and then navigate to the "Account and Settings" page.
2. Make sure that "Multicurrency" is turned on and click on "Manage Currencies"
If multicurrency is not enabled then make sure that you enable it by enabled the options below.
3. On this page you are shown a table with the active currencies enabled on your account. To add additional currencies, click the "Add Currency" button and scroll down to the currency that you wish to add.
Now that you have multiple currencies set up in QuickBooks Online follow this article on how to reconcile foreign currency denominated settlements in QuickBooks Online.