How do you customize a theme in Shopify?

To customize a theme in Shopify go to your Shopify admin panel, access the "Themes" section, and choose your desired theme. Click "Customize" to access the Theme Customizer. Customize various elements such as colors, fonts, headers, footers, and content layouts using the sidebar options. Preview your changes in real time and save them when satisfied. Finally, click "Publish" to make your customizations live on your online store.