Edit your theme's liquid files at your own risk. 

Editing the theme requires some understanding of how HTML works and ideally also how liquid works.

Click on "Online Store" in your Sales Channels in the Shopify admin.

Then click Themes.

In the section "Current theme" you'll find your live theme.

Create a backup of your theme before you make any changes. 

In the "Actions" menu, select "Duplicate" to make a backup.

You can now click "Edit code" to start editing your theme

Create a separate file and paste the content. Repeat for every file you plan to change. Better safe than sorry!

In the list of backup themes, select the one you want to restore and select publish.