# Update the configuration

This guide describes how to dynamically update the configuration of your Rebilly Instruments payment form in order to change the locale (language).

The Rebilly Instruments library provides an `update()` method you can use to modify any configuration property at runtime. This is useful for:

- Changing the locale of the payment form.
- Updating payment amounts dynamically.
- Switching between different payment methods.
- Modifying form styling or behavior.


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Prerequisites
To complete this guide, you need to have:

- A basic payment form using the Rebilly Instruments library.
- Your publishable key, organization ID, and website ID.


If you have not set up a payment form using the Rebilly Instruments library, see [Get started guides](/docs/dev-docs/get-started-integrate-payments).

## Step 1: Add the UI element

Add a button to your HTML that users can click to change the language. This button triggers the locale update.

## Step 2: Implement the update logic

Add code to handle the button click and update the configuration of the Rebilly Instruments library.

Your existing `RebillyInstruments.mount` code remains unchanged. This step shows the initial setup for reference.

Create a variable to track whether the locale has been changed. This helps toggle between languages.

Add a click event listener to the button. When clicked, this triggers the locale update.

Toggle the locale state and determine the new language. Also update the button text to show the current language.

Call the `update()` method to change the locale and re-render the payment form with the new language.

All mount parameter properties can be updated using this method.

For more information, see [RebillyInstrument.update()](/docs/dev-docs/reference-rebilly-instruments#rebillyinstruments.update).