after I open the file with cheat engine and selected the boxes as instructed, I see no button like "apply" or "ok" to finalize the settings?You need to open it with the CheatEngine. Then when the program is running you need to click on the upper-left button "Process List" and choose this game. Obviously, you've got to start the game first.
Once all the above is done, you can choose the desirable cheats on the list. However, half of them don't operate on the newest build.