Here’s how you can quickly replace the older style with new, asynchronous style.
Go to your original Widget. Click the Copy button. (You can also click the Copy button under the Actions section of the Widgets List.)
This will automatically create a copy of your Widget, with everything the same as it was, but with asynchronous code.
Copy and paste the new code in place of the old on your website.
Now, you’re all set. (You may notice that your page loads and then the button appears.)