For integrating live chat button with your PrestaShop theme directly you need to have access to your PrestaShop files via standard FTP client or the cPanel File manager.
Please use the following guide to add the chat button to your website theme.
Grab the code for your chat button. For this log into your Provide Support account Control Panel, follow there My Account / Chat Button Codes page and choose 'Fully Featured Chat Button Code with Uploadable Online / Offline Images'.
Open your PrestaShop files through FTP or cPanel
Now follow themes > classic > assets > js folder or themes > theme name > assets > js folder if you use a custom theme
Edit there "theme.js" file
Insert your chat button code at the very bottom of the file and save changes
The chat button will appear in the position defined in your account settings
You can adjust the position of the chat button, its form and color, as well as the chat window appearance on the Account Settings / Live Chat Window page