The best way is to have pictures on your hard drive.
For a profile picture, the size seems to not matter. My current profile picture is too big to put in a post.
Go to your profile and browse your hard drive for a picture and then open it.. that's about it.
For pictures in a post, see the sticky thread at the top of this forum. Most folks have had little problem getting the images loaded.
Good to see you here. Adios,