In the presto movement, how do I play the notes with a slash through them?

If you are referring to notes such as those in measures 182, 186, & 187, those notes are ornamentations commonly called grace notes and are more formally named Acciaccatura. Essentially, it is simply a very short note (played very quickly) that preceeds the main note to which it is attached.

See a full explanation with examples here:
http://en.wikipedia.org/wiki/Ornament_(music)#Acciaccatura