Ok, since you've said that the user input needs to happen repeatedly, that tells you that you want the user input to happen inside a loop. Since you've said that you want to keep looping *while* a certain condition isn't met (the user says 'no'), that tells you that you want a while loop.

Personally I like to use psuedo-code - something that is half-way between English (or whatever your native tongue) and code - and then gradually replace the pseudo-code with real code. Here's how I'd start with your assignment:

    user_wants_to_continue is 'yes'
    while ( user_wants_to_continue is not 'no' ) {
        prompt for and get product_name
        prompt for and get quantity
        prompt for and get price
        store product_name in array
        store product_name, quantity, price in hash
        prompt for and get user_wants_to_continue
     }