You can top-up your Mynk account through your bank card. You will need to register it on the "Account" section, and then you can easily recharge Mynk with a few clicks.
To send money to one of your friends, click on "Send" on the homepage. You will just need to enter the amount and their phone number before confirming the transfer
You can withdraw your money at any time by sending it to your bank account. To do so quickly, you will need to register your account details on Mynk.