When you write a new post, there is a box you type in.
Above the white box there are many buttons for different functions. Look for the one that looks like a paper clip.
Click on it.
It will bring up a separate window, and you can press the "browse" button to search for the folder your picture is in, then click the picture and press the submit button.
Return to the popped up window and press submit and it should start to load and eventually load up and say the picture is attached.
It will not show on the original page, but then just submit your post and it will be there.