Open Burp's browser and log in to your account. Submit the "Update email" form, and find the resulting request in your Proxy history.
If you're using Burp Suite Professional, right-click on the request and select Engagement tools / Generate CSRF PoC. Enable the option to include an auto-submit script and click "Regenerate".
Alternatively, if you're using Burp Suite Community Edition, use the following HTML template. You can get the request URL by right-clicking and selecting "Copy URL".