choose the picture first dear
then copy the link
after that paste it on the 'main picture' coloum
then paste it.
if you want to use for whole chapter
click the mark on the little box above the link
done
but not every link could use just few site link
you will got know when you try to post it
good luck dear

Try dragging the photo directly onto the space used for typing? That's what I do since I don't use photobucket