Update page.mdx

apps/portal/src/app/connect/account-abstraction/infrastructure/page.mdx

@@ -27,6 +27,42 @@ With a thirdweb API key, you get access to bundler and paymaster infrastructure
 
 To support a chain not listed, [contact us](https://thirdweb.com/contact-us).
 
+## Using Paymaster & Bundler URL
+
+To use the Paymaster & Bundler URL for thirdweb, you can follow the guide below:
+
+### URL Pattern
+
+The URL pattern is predictable for all chains and is used for both paymaster and bundler operations:
+
+```
+https://<chain_id>.bundler.thirdweb.com/v2/<thirdweb-client-id>
+```
+
+Replace `<chain_id>` with the appropriate chain ID and `<thirdweb-client-id>` with your thirdweb client ID.
+
+### Client ID in Header
+
+You can also pass the client ID via the header:
+
+```
+x-client-id: <your_thirdweb_client_id>
+```
+
+### Frontend Calls
+
+For frontend calls, the calling domain needs to be allowlisted. This can be done from the thirdweb dashboard in the API key settings.
+
+### Backend Usage
+
+For backend usage, the secret key is required as a header, and the client ID can be omitted:
+
+```
+x-secret-key: <your_thirdweb_secret_key>
+```
+
+Make sure to replace the placeholders with your actual values. This guide will help you set up and use Paymaster & Bundler URLs effectively with thirdweb.
+
 ## Using a Custom Bundler
 
 Smart accounts are free to use with your own account abstraction infrastructure. To use your own paymaster & bundler,