To enable this provider, you need to enable apns-binary-api bean within push component configuration scope.

Example. 

push () {
    'apns-binary-api' () {
        # APNs configuration here
    }
}

APNs binary API provider will not work properly without certificate file required for authorization by APNs and password to decrypt this certificate file. You need to get certificate using Apple Developer Account.

When you have this certificate, you need to pass path to certificate file as cert-file property and password as cert-password

Example for /etc/apns-cert.p12 and Pa$$word. 

push () {
    'apns-binary-api' () {
        'cert-file' = '/etc/apns-cert.p12'
        'cert-password' = 'Pa$$w0rd'
    }
}

By default this provider uses many connection to APNs for sending notifications which equals to number of available CPU cores. If in your use case it is to small or too big number, you can adjust it by setting value of pool-size configuration property. Setting it to 5 will make sure to use only five connections to APNs.

Example. 

push () {
    'apns-binary-api' () {
        'pool-size' = 5
    }
}