Currency Converter HQ can be uninstalled by deleting the app and reverting your currency formatting settings. Delete the app my navigating to Apps (in the shopify dashboard) and clicking the trash can icon next to the app. Revert your currency formatting settings by heading to the Settings > General page. Once on this page scroll down to the Store currency section. In this section you will find a link Change formatting, click it to open up its options. In both the HTML with currency and HTML without currency fields remove on the left and on the right. Save your settings to complete uninstallation.