Chisca - perhaps post some of your code to give us an idea of what you have tried, and then we can provide some guidance on how to continue. Are you reading all of the data in at once, or are you trying to just look for specific entries within the files?
I suggest that you try the former (use importdata, or textscan, or xlsread depending upon the file type) and then look in the first set of data (user info) for all rows whose first column corresponds to the known user id (you could sort this data beforehand). Then look in the second set of data (the movie info) and find all the movie information corresponding to the movies that match to the user.
