At the left side of each line, there will be a key signature. All of the sharps you see there mean that that key will be sharp each time it appears in the music (unless there is a natural sign, which cancels the sharp). And, if there is a C# in the key signature, then ALL of the C's are sharp, not just the high C. This is a difficult piece to read because, even if you've got the key signature down, there are many accidentals - extra sharps and cancelled sharps. There are also many B#'s, which can be confusing to a beginner.
Sorry if this information is obvious to you already, but from your question it seems like maybe you didn't already know it. Hopefully, it helps.