ok so under the actuall post you will see a box that says 'Attachments' in the top left corner with a little folder and green arrow in it. To the right of that you will see a text field with a browse button, click it and look for the picture, then click upload. The box will change to a loading box and then once it has loaded there should be a drop down menu that says 'Manage Current Attachments (1)' your picture should be in there and to the left click the icon with the green plus sign on a little page and it will add your picture to the post