To add more currencies to your site, refer to this documentation.
Enable a currency selector for your store
Once you've added your markets, you'll want to enable the currency selector for your theme so that customers can select their local country or region and your store displays their local currency.
Steps:
From the Shopify admin, go to Online store > Themes > Customize.
In the Header section, enable the 'Enable country/region selector' setting.
Note: This setting is for the Mobile layout, and this shows a country/ region selector on the menu drawer.
In the Footer section, check the option 'Enable country/region selector' in the Footer on both views.
Save the change.
Our themes don’t support placing the country/region selector in the mobile header due to limited space.
If you require this customization, you'll need to work with a developer.