Including OggChat in your Shopify Account is easy. Just follow these instructions on how to copy the chat widget into your Shopify website.
Login to OggChat
Login to your Shopify Account
Select Theme --> Template Editor in the top right-hand side
Under the Layouts heading, select "theme"
For OggChat Tab Widgets (the default), scroll to the bottom and copy the OggChat Widget code from the OggChat Dashboard right before the </body> tag.
For OggChat Buttons or Custom Online/Offline Buttons, scroll to the location in the template page where you'd like your button to appear. Copy the OggChat Widget code to this location.