Recommended Method
On the Shopify app store, you can find language apps which can translate your store into right-to-left (RTL) translations.
Advanced Method
If you're confident in editing your Liquid code, an alternative method to using translation apps is to create an RTL template.
When you purchase a theme, it is complete with certain templates (e.g. the Collection page template, or the Product page template). However, Shopify allows merchants to create and replace your theme's templates by creating a new one.
Read: Shopify's help pages on Templates.
If you're not entirely confident with making these changes yourself, we would definitely recommend approaching a specialist in custom coding.