Code review comment for lp:~clissold345/ubuntu-docs/fix-for-1599264

I revised "Add an account" some more. Eg I found I did want to use the term "online service" after all. I tried to make the "permission" steps clearer. In the first the user tells the online service to allow Ubuntu access and in the second the user gives Ubuntu permission to access the online account. And I made other small changes too.

I'm planning to do the "power critically low" changes later today.