Hi,
Uploading images in your blog post is very easy, But today when i started my blog post i got new editor option which was never i seen in Steemit(May be i was there but i never notice).
With Editor tools you cant upload images it ask you for url. which ask for the images already uploaded on server.
In below blog post everything given properly for upload images from external source.
But if you are trying to upload images within the steemit post you need to switch the editor which i realize today.
Just switch your selection option and you can upload images in steemit post itself.
I know this not something new or difficult for you. but i thought most may not aware about this.
Thanks