we're not allowed to discuss content of exams until they're done, and the ISA is a tricky one as some people will have already sat it, and there are others like yourself who havn't dont it yet.
Are you studying at home? where are you doing your ISA? At college, the teacher can tell the class the general subject area that is going to be investigated, one week before hand at the most.
From experience, I dont think the actual practical bit takes a lot of preparing for. you just go in there and follow the instructions. honestly. the written element tends to ask about experiment design, results graphs, errors / uncertainty etc, rather than hard physics.
you should try to have a chat to the person who is running your isa.
good luck, and don't worry!!