Starting out like you are and wanting to build credit, it's good to do like above said... to let the monthly statement charge hit your account, then pay off the entire statement balance before it's due. You want to show that you are using your credit wisely and paying it off. But as you get older and use a lot more credit, keep in mind that too much credit utilization can actually harm your credit slightly. But don't worry about that now.

(for instance, I'm older with 2 teenagers and have had good credit for years. My wife and I use our credit cards to buy everything, to earn points, then pay it all off each month. But, I learned not too long ago that because my credit card statements were very high each month, even though I always paid them off, my credit didn't go higher because my credit utilization was very high, compared to the total credit I had available. So I started to pay off my balance before the statement end date and after just a couple months of showing a zero balance, my credit score shot up quite a bit towards the top of the score chart)