## Add

`UserAddResponse express().users().add(UserAddParamsparams, RequestOptionsrequestOptions = RequestOptions.none())`

**post** `/v1/express/{expressCustomerId}/users`

Associates an existing user with a customer, granting them access to customer-specific resources and studies.

### Parameters

- `UserAddParams params`

  - `Optional<String> expressCustomerId`

    Unique Express customer identifier. Format: cus_{32-hex-chars}

  - `String userId`

    User ID to add to the Express customer. Format: usr_{32-hex-chars}

### Returns

- `class UserAddResponse:`

  Standard success response with optional message

  - `boolean success`

  - `Optional<String> message`

### Example

```java
package com.avara.example;

import com.avara.client.AvaraClient;
import com.avara.client.okhttp.AvaraOkHttpClient;
import com.avara.models.express.users.UserAddParams;
import com.avara.models.express.users.UserAddResponse;

public final class Main {
    private Main() {}

    public static void main(String[] args) {
        AvaraClient client = AvaraOkHttpClient.fromEnv();

        UserAddParams params = UserAddParams.builder()
            .expressCustomerId("cus_1234567890abcdef1234567890abcdef")
            .userId("usr_1234567890abcdef1234567890abcdef")
            .build();
        UserAddResponse response = client.express().users().add(params);
    }
}
```