Not sure if the screen you see when you are posting has a tab "go advanced". Click on that. Then scroll down to "manage attachments". Click on that. Should open a screen that has a tab "add files". When you click on that, you should be able to find the pics on your phone. Select the pictures you want. They should download to an area that will have a tab "done". At that point, they should show back up in the area that you clicked " add files".... That should now read "upload". Click on that. Should work. Then you could click on "preview post" to make sure. If ready, click submit post.
Again, I'm not sure if it is the same for an android device, but should be similar.