Just open your facebook page and click on setting.
After that, you will see the messaging optionin left side, you have to click there.
Now after clicking, you will be redirected to this page where you will see option of Adding Messenger To Your Website. Just click on Get Started.
After you clicked, you will see the page similar to below mention screenshot. Click on next
Now set the custom message according to your requirments. See the below reference image for more better understanding
Click on next after saving your Greeting Message and change the chat icon color according to your comfort
Now, again click on next and submit the domains ( web address ) where you want to show this facebook messenger chat plugin . Click on code and copy it and just click on finish.
Now before you finish, there is a reminder above the facebook live chat code that this code should be paste after each page of website but in our case, We only have to put in one place,In edit html theme section of blogger dashboard. just type Ctrl+F & search <body .
After getting body open tag, paste the code after the <body ( open body tag ). Now search class=’fb-customerchat‘ , On the left side of this class, you will have to replace attribution=setup_tool fromattribution=’setup_tool’.Now save your theme and open the blog/website & comment that is it working on your blog or not ??