help about adding permissions on android?

so i am trying to add a permission for my android app

i'm trying to add permission so it could use the internet, i have located the manifest on my project folder: C:\Users\Public\Documents\Unity Projects\Plank!\Temp\StagingArea

in the StagingArea folder contains the AndroidManifest and AndroidManifest-Main

i edit the AndroidManifest using notepad or wordpad, then i add the permission after the permission :

so basically like this

then i save the notepad, and when i build and run the project i get nothing when i check the manifest again the permission for internet is just gone nada, and sometimes i get an error that basically says that the process tried locating something that is not there and i have to tryagain or forcequit and when i quit the manifest returns without the internet permission... how do i add this internet permission its so hard, i made apps before using eclipse and it was easy as hell to add this permission in the manifest... but now i just don't know what is wrong... please help thank you.