Login to your CometChat Admin Panel with your Credentials.
Now from the left menu click on "Settings->Editor"
After that copy below Code and paste it in "Text Editor" & Click on "Save" button.
From Left Menu Click on "clear cache".
Copy And paste below code in your site page.
<button type="button" onClick="cc_testCometChat();">Click Me </button>
Once the above code has been pasted on your site. Kindly visit to your website where you have mentioned the above code and press the button that which says "Click Me".