Edit .exe Or .dll Files?

I have been wondering for a while, what if theres a game and i want to edit it's dll files or exe files? theres a game called amnesia and i want to add a extra button on the game's launcher, but i do not know how, i managed to download a couple programs that can do things like take the exe appart, or read some dll files but not with much success, if i take appart the exe i get 3 files, .text, .data, .rdata, and a folder called .rsrc with icons of the exe in it, i see the icons, sadly i havent found any way of opening the text or data files, the dll files ive managed to open, read and edit save, but then it doesn't change anything or if i modify the exe code it saves but then doesn't launch