To play notes on a trombone you need to move the slide out and in. There are seven positions available, unless you have short arms then there may only be four and you should think about swapping your trombone for a trumpet (or a flute if you like your neighbours).
Each slide position can produce several notes depending on how hard you blow. High notes are really difficult to play on a trombone which is why a flute is a much better instrument. Also a flute is easier to carry around.
A really gross thing about playing a trombone is that the tube fills up with spit as you play, making it sound as if you were playing it under water in the swimming pool. There is a little tap on their end of the instrument to allow trombonists to empty the spit onto the floor at the side of their chair. By the end of a concert the floor around the trombone section can be quite slippery. Flute players have much less of a problem with condensation and normally get rid of it by resting the end of the flute on their knee and gently tapping it. The only drawback to this method is that after a concert, flautists look as if they have wet themselves.