Google tag manager helps you to manage all your tags in one place. If you haven't installed GTM on your website, then follow this link-
Copy the code snippet from the bot settings page in Mailcastr dashboard
In your Google Tag Manager Dashboard, choose the container (site) that you want to install Mailcastr on
Choose to Create a New Tag
In the pop-out with an Untitled Tag, choose to create a “Custom HTML Tag”
Paste the Mailcastr code you copied earlier into the empty HTML box:
Name the tag.
For your Trigger, choose to fire on “All pages” unless you’d like to do something else specific to Tags and Data Layers you've created within GTM ?. You can always customize where the Chat Widget shows on your site from within your Mailcastr dashboard
After saving the tag, you're not quite done. Remember to Submit your changes permanently (and preview them first if you would like).
After you submit your changes, you can describe your Version and hit Publish. You're all done now!. Try the website in an incognito window and try interacting with the bot. Check the responses in the Mailcastr dashboard. There might be some small delays in updating the response.