If they're saved on your computer, it should be as simple as clicking on the icon with the blue up arrow...
That should bring up a new window that looks like this...
Click the gray "Choose file" button and select the photo you want to upload. Then click the brown "Add file from your PC" button. It will then display the image below and you can rotate it one way or the other as needed. Then click the brown "All done" button and your post will show the computer code necessary to embed the photo in your post. You can preview how the image will look within your post by clicking the brown "Preview Reply" or "Preview Post" button at the bottom of the text window.