You can install GtChatPro on Blogger very easily.

Please sign up for GtChatPro

You will get the chat code in the channel section go to channels  > Add New. 

1)  Log in to your Blogger.com account and navigate to the dashboard for the blog where you want to add the code.

2) Click on the "Theme" button on the left-hand side of the dashboard.

3) Click the "Edit HTML" button in the template editor.

4) Use the "Find" function (CTRL+F) in your browser to locate the </body> tag in the template HTML.

5) Before the </body> tag, paste your code. Make sure the code you enter is valid HTML, JavaScript or CSS.

6) Click the "Save template" button to save the changes.

Now, Preview your blog to make sure the code is working as expected.