When you open your X-Account, you can toggle between receiving interest in kind or interest in WXT. ‘Interest in kind’ means that you’ll receive interest in the same currency your X-Account is attached to. ‘Interest in WXT’ means that you’ll receive interest in WXT and guarantees an extra 4% on top of the existing interest rate.
If you selected to receive interest in kind, you can always upgrade your X-Account and start receiving interest in WXT at a later date. All you need to do is to select ‘Upgrade option’ in the X-Account preferences.
Please note that if you choose to receive interest in WXT, you won’t be able to switch to interest in kind. You can, however, open another X-Account on the same currency and toggle ‘interest in kind’, or simply close the existing X-Account and open a new one.