Jill for the sale items go to the classified area- list them and a Moderator will find it and either approve it or send you a reason it cannot be accepted
it will only take 10 pics the first time- so post those then "reply" with the next 5 items if you are selling 15
For signing in have you tried the leave me signed in option ? Next time you have to log in - next to that should be a box that you can click and that will help keep you logged in
Like I said I have gotten the do you want to leave this page message when posting an answer - at first it rattled me , but now I just click yes , it posts the reply and off I go - so can't explain why it is not posting