You get a voucher which has a qr code and serial number that resembles a phone top up voucher. You can redeem this in two ways.

Scan the qr code which works automatically with certain wallets, bluewallet for on chain and phoenix/wallet of satoshi for lightening and the SATs are sent to a fresh address with no further action required.

Or

Goto the site and input the serial number on your voucher and an address to send to.

It is seemless.