Click “Settings” on Menu in the top menu bar
Click on "Sites" right beside "Global settings"
Click the code icon 2nd Icon in the line
See image here:
https://www.screencast.com/t/gLusfQBG
Copy the Widget Code
See basic video here: https://www.screencast.com/t/XJTgniLaEoLS
Now login to your Shopify administrative panel.
Click on "Online Store" in the navigatin menu on the right
The view will default to Themes
On the left, there will be an "Actions" menu. Click on it and select "Edit Code"
Video: https://www.screencast.com/t/4S0a7TknYoAR
Static Screenshot: https://www.screencast.com/t/T6HmXRaW
In the resulting screen, click on "theme.liquid" under "layout at the top. The code that appears woill be the basic body of your web pages.
At teh bottom of the code block, there is a </body> tag.
Paste your Hosted.Chat widget code just above this line and click "Save"
Your chat widget should be published now. You can see it immediately usin the "Preview" Button, but your live site may take up to 15 minutes to update and show the new chat bubble.