To find the file you must know what the file is and then go to start and press type in the file name and it should appear. if it doesnt you should type in adobe after effects into the search bar and then go into the after effects file and type in the file name in the search bar and you should find it then but if it isnt there then you should reinstall the program then the file should be there but if they arent then there is something wrong with the disc
In the time line there should be a colored bar beside the image name. All you have to do is drag the ends of the colored bar to what ever time you want it to begin at and what time you want it to end at and i think the hot keys are M for the begining and N for the end. hope this works