In Hungary we have a meeting for translators, and we've just held the 2nd one. Unfortunately I couldn't attend, but I've made a video regarding the matter. I could show you the video, but it's in Hungarian language.
Regardless of that, here's what I've made:
BASIC RULES OF A TRANSLATION:
1. Always make a copy/backup of your files in case you mess something up.
2. Find a very simple part of the game (like the main menu, options, the first text you see...etc) and edit that one to see if you can edit the text or not.
3. Try to change one letter (like "Play" could be changed to "Plai" or anything, maybe "Exit" or "CooL"...etc), and see if you change it then it also changes in the game (and can the game be run at all)
4. Try writing shorter or longer text ("Go" instead of "Play", or "Start", because one is shorter and one is longer), and again, see if the game still works
5. Try out special characters. Because I'm Hungarian, I try out my unicode characters to see which ones work and which ones doesn't (like "íéáőúöüóű").
That covers the basics, let's see how I translate these games:
1. Start the game, and look for an easily editable and viewable text (like the one I've mentioned above, the "Play" one)
2. Exit the game, and open ALL .assets files in Notepad++ (the text could be in resources.assets, sharedassets0.assets or sharedassets3.assets, but I've seen some different results)
3. Now CTRL-F and search your text in all documents. Some documents should pop up and you can see if it contains said text or not. If nothing is shown, then maybe you need to choose a different text and search for that
4. After you've found out where it stores your stuff, then open up that .assets file with UnityEx. By using it, you can extract all files in a folder.
5. Open said folder and open all files in Notepad++, and search for your text. It should give out one file, maybe with a weird extension (like -5, -49, -52...etc).
6. Edit said file and save it, then import it back in with UnityEx.
7. Start the game, see if it works.
If by any chance it doesn't work, then maybe the game has pointers assigned to it. Pointers can be edited with HEX Editors (like HEX Workshop), and they determine how long a certain text can be. If you open up a file and look around it's bits and bytes, you should see something like this: "0004000something". Those 0-s divide the text in the file, and that 4 is a value which determines how long the next text segment will be, which is "Play" in our case, and that's 4 character long.
That's all for today, don't know what else you need, but if you have any questions feel free to ask.
Also I know you've posted like a month ago, but I do hope you are reading these forums and that this little tidbit of text will be helpful for you (or for anyone else)