1. Login to WHM and click on "WHMAMP Reseller Addon" from the left side.
2. Click on "Upgrade" > "Upgrade cPanel to Reseller" > and make that user to Reseller first. Now if you want that Reseller to grant Master Reseller permission, then again click on "Upgrade" > "Upgrade Reseller to Master"
You can only make a Reseller to Master, if you have an active ALPHA MASTER RESELLER plan with us.
For any help, you may contact with our support team anytime.