I followed the instructions of the tutorial, too.
If everything is done as written there, you should have an error about an unknown function, because there is a typo in the function name: MyFirstAddOnInit
ialized
Therefore I guess you have to check something else: Did you enable "Show File Extensions"?
Because ESO silently ignores all files which can not be loaded.
If your files real names are "MyFirstAddon.lua.txt" or "MyFirstAddon.xml.txt" you will not get a load error.
There is another first addon example:
Hello World