1:- Extract the zip and you will get a directory named byteseller inside that directory there will be modules directory.
2:- Upload The Modules Directory to root of your whmcs installation .
3:- Login to your whmcs admin area and navigate as Setup->Payments->Payment gateway.
4:- Click on tab "All Payment Gateways" and Search for ByteSeller and click to activate .
5:- Click on "Manage existing Gateways" tab on Top and Look for Byteseller Setting area .
6:)Add the Respective details and Save the Setting area. and your gateway is configured.
7:- After activating payment gateway you need to get the Notification and return url added in your byteseller account .
In order to do so you need to contact the byteseller support.Without adding the notification Url your whmcs nvoices will not be marked paid .
8:) Notification URL Will be like this
https://YourwhmcsUrl.com/modules/gateways/callback/byteseller.php
9:) Return URL will be the clientarea url of url .
https://YourwhmcsUrl.com/clientarea.php