The rules of photo hosting sites change constantly, but we'll try to show how to add photos here from various other sites, as you can't directly upload photos here (we don't have the storage size to allow that).
FLICKR -----------------------------------------------------------------------------------------------
Flickr doesn't really want you to post images directly to other sites, like this one. They want you to instead post a link back to the actual Flickr page.
You can bypass this though.
1. On your image's page, click on the three dots ( ... ) on the right side and choose DOWNLOAD/ALL SIZES.
2. Click on MEDIUM 800.
3. Right click on the image and choose COPY IMAGE LOCATION.
4. Flip back to your MFK post. Hit the image button (Img).
5. Hit control V to paste the image location in between the two image brackets. Done.
PHOTOBUCKET --------------------------------------------------------------------------------------
I don't have direct experience here, so if this isn't accurate, let me know. But, I think it's much simpler.
1. Get a free photo hosting account.
2. Upload pics.
3. Copy the [img] code the site gives you into your post here.