We are learning (and making mistakes

) about posting pictures on this forum too, hope this helps others.
Upload your pic(s) to the hosting website of your choosing.
Top Ten Image Hosting Sites
http://www.ebizmba.com/articles/image-hosting-websites
Many hosting websites will provide you with the forum sharing code already input, copy then paste it into the post you are making.
It would look like:
[img]xxxxxxxxx.jpg[img]
Good info "webslave" posted Sep 03, 2012 “photographs should be resized to around 500 pixels in width, 620 max, so that server space is conserved, scrolling is avoided and everyone can see them.”
If the image hosting site didn't give you the option to shrink the picture and it is too big these sites will do that for you.
http://www.picresize.com/
http://www.shrinkpictures.com/