A bitcoin wallet on a smartphone (like mycellium) is optimal but not required.

Go to the atm, enter your phone number, it sends a confirmation code then you're in. Then it asks for a btc address to send the coins to. Mycellium and most other wallets generate a qr code that you can scan in the atm. The recieving address should then be entered automtically into the atm there are just too many digits to fuck around.

Now you can insert the money and watch it send to your wallet right away.