Question about my Capital One billing cycle?

I just got a capital one platinum card about 2 weeks ago. It has a $500 limit and I used it at target for 23 bucks. I really want to pay it off before the payment is due so there isn't any interest on it. I keep trying to online and i get an error message that says "We're sorry, but our system experienced an error while processing your request. Please try again later. If the problem continues, please call us at 1-866-750-0873. We're here to help you 24 hours a day, 7 days a week. (Ref. No. XXXXX-XXXX)" I have a feeling it might have something to do with the fact that in the "payment due date" field, it says N/A. does this mean I can't make a payment until the due date is announced? Can i not pay it off early normally, or is this just because i haven't gone through my first billing cycle yet? am I screwed and will I always have to pay interest? My mother said if you pay it off before the due date then you don't get charged interest... So I got a credit card to build my credit... but I don't want it if interest is completely unavoidable.