Upload the new XML file to your account. You can reuse the filename and overwrite the existing file. But to allow for easy rollback in case of issues, use a new name to create an XML asset in your account. Upload the file.
If you used a new name choose Setup > Application Setup - Publish Setup > Image (Serving|Rendering), depending on the context where the Rules will be applied (/is/ or /ir/). Scroll down to find the setting for the Rule Set Definitions File and use the browse button to select your new file.
When you are done, save the settings and run a publish of the appropriate type.
Once the publish completes, clear any previously live URLs from cache to see any changes. Any URLs that were previously returning an error work once the publish completes.