You don't need any other passwords to post pics all you need to do is
Click on the "Full screen reply button" at the bottom of your screen
Then click "file manager"
Then click "Browse"
Select your photo then click "add file"
Repeat the last two steps for each photo
When you have enough photos click "Done adding files"
and it should be fine, if the photos don't load it means their too big and you need to minimise the photo's.
regards