The same way you read any other sheet music. We can't teach you how to do that here. There is one tricky bit: Saxophones are "transposing instruments" ... playing saxophone music on a non-transposing instrument like a piano will result it in being at the wrong pitch.
Search "Apologize alto saxophone sheet music." You should get some results. If you want free music, sometimes finding it is harder. If you can't find music specifically for alto saxophone, you could always find the concert pitches (such as vocals) and transpose.