You can post a picture from your hard drive.
You cannot do it from the Quick Post window, so click the "Go Advanced" to get to the advance window.
Make sure you fill in your title etc. Scroll down to reveal the rest of the page and look for the "Manage Attachments" button. The rest is self explanatory. Also watch the file size to make sure you are not exceeding the file size limit.
Hope this helps.
“Only when you drink from the river of silence shall you indeed sing. And when you have reached the mountain top, then you shall begin to climb. And when the earth shall claim your limbs, then shall you truly dance.” ~ Kahlil Gibran