Usually you can find all the information you need for this operation in the user's manual or the service manual that are given to you when you purchase your MacBook. But if you lose them or buy your device from another person who did not have them, you will have to settle with the electronic version of the latter that you can find here. If you access this link you will be able to read and also save a copy of this service manual for your MacBook pro, as it can be very useful for the future in case it gets damaged again.

You will find the replacing MacBook Pro keyboard instructions on page 13. If you are a beginner in this business and have not disassembled a macBook before, you will find a detailed tutorial here, that also shows you the location of all the screws you need to remove when replacing the keyboard.
After you remove the lid on the back of your MacBook, you will see a plastic backing that protects the keyboard. It is very unusual when compared to other laptops, but it is very beneficial for you as a MacBook user. It protects the contents of the MacBook case and preserves them for a longer use. Just peel off this protective cover and them remove all the screws and all the tiny components that hold the keyboard in place and after you succeed this replace it with the new keyboard and make all the movements in reverse. If there is no need to replace the keyboard, but only to clean it, do your job carefully and then put everything back in place. In order to avoid spilling accidents you can buy a protective cover for your keyboard and it will save it, since it can be a lot easier taken out and washed.

When there are only a few keys popped out of your MacBook there is no need to remove the whole keyboard. You just need to place them exactly in their place and then press carefully, but firmly and they will be fixed again in no time.