You go on the website, order your stuff. When the normal payment screen that comes up, instead of Mastercard or visa, you choose "Cash". You'll then be sent a text message with a number (or the number appears on the screen if you don't have a phone). You go to any ATM anywhere in the country, put that number into the ATM, feed the cash into the coin and note slot, and then your goods will be ordered.
The same system is used for paying taxes in cash, utility bills in cash, etc.
They can do refunds in cash using the same system.
You do pay a fairly hefty (10% if I remember correctly) fee for using that service though.