Changing the main image in an instructable you have published/ submitted to contest Answered

f.e., go to :

https://www.instructables.com/you?show=INSTRUCTABL...

click on EDIT (next to title of your post)

there pull down from the *add* menu:

*photos*

then just drag the new image from your desktop etc into the pop-up-window

upload it like any image you have done before, ok it,... the image will appear as thumb in the top-bar

now drag the old image back into this very top-bar, and drag the new one down to where you just pulled the old one from.

save the edit

done