Here’s Amsterdam’s info notes on how to operate with the machines:

Step 1: Enter the four-digit number on the upper key pad corresponding to your destination listed on the left side of the machine. The code for central station is 1000. The code going to Schiphol is 1117.

Step 2: Press the lighted button marked “2e Klas” for second class or “1e Klas” for first. (Note: there is almost no difference between first and second class travel in Holland)

Step 3: Press the “Vol Tarief” button for a full tariff or “Korting” if you happen to have a discount train card.

Step 4: Press “Alleen Vandaag Geldig” if traveling today or “Zonder Datum” if you want your ticket to be valid for some other date.

Step 5: Press “Enkele Reis” for a one-way ticket or one of the “Retour” buttons for a return ticket valid for a return trip on the same day (or “Weekendretour” valid from Friday 19.00 to Monday 4 o’clock).

Step 6: Insert the amount indicated.

Step 7: Collect your ticket and any change in the basket near the bottom of the machine and hop aboard your train.

http://www.amsterdam.info/transport/tickets/