First. You need jr.member rank or more
(see more here https://bitcointalk.org/index.php?topic=2818350.0 )
2: sign up a account https://imgur.com
3: upload your picture on imgur.
https://i.imgur.com/DbWsGmB.png
4: wait a minutes and f5 page
5: copy BBcode and paste in the BCTpost
like this:
https://i.imgur.com/TPwjfLV.png