It will take some practice to be able to play some of the higher notes simply because you need to exercise your lips so they have the strength to buzz faster. It will take some time to train your lips, but you should play too much at once, or play too loudly or higher than you are able to comfortably. There are many blood vessels in your lips, and if you stress them too much, they will burst and swell up. Once you are able to play up to a high C, you should learn a scale. The first scale most people start out with is the concert B flat.
All scales have the same format.
They go up in steps and half steps. One full step is a jump from one note to another note higher than it is. A half step is simply half of a whole step. A half step higher then a C is a C sharp. Sharps and flats simply raise a note up half way to the next note, thus making a C sharp equal to a B flat.