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Go to a picture hosting site such as photobucket.com, upload your picture, then copy the direct link from there directly into your blog :-)

@shammyshiggs is right!

BUT

Sometimes the site Doesn't reconise the photo so you have to use markdown:
! [] ( )
Note: the are NO spaces between them.
For a better understanting I made a tutorial with clear example :
https://steemit.com/steemit/@cynetyc/how-to-upload-images-an-videos-on-steemit
And check olso on how to center in your post the image and videos :
https://steemit.com/steemit/@cynetyc/how-to-center-images-and-videos-on-steemit