You must create API Keys for each section, merchant or micro payments(faucet).

Creating API Key for Merchant: Merchant Section -> Merchant API -> Generate new API Key
Creating API Key for Micro Payments: Micro Payments Section -> Faucet Dashboard -> Add new Faucet

Provide generated API Key to HTTP Authorization Header

Merchant API Example:

curl "https://anonwallet.net/api/v1/API-METHOD" \
     -H 'Authorization: YOUR_API_KEY'
<?php

$auth_token = 'YOUR_API_KEY';

$headers   = array();
$headers[] = 'Authorization: ' . $auth_token;
$curl      = curl_init();

curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);

Micro Payments API Example:

curl "https://anonwallet.net/micro/api/v1/API-METHOD" \
     -H 'Authorization: YOUR_API_KEY'
<?php

$auth_token = 'YOUR_API_KEY';

$headers   = array();
$headers[] = 'Authorization: ' . $auth_token;
$curl      = curl_init();

curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);