When you make a new post, go down below the text box to the Manage Attachments button and click on it. A new window will open up, where you can browse your own computer to find the picture you want to upload. There are limits on the picture size, for a regular jpeg picture it needs to be smaller than 78kb.
If the picture you want to include is too large, you'll have to reduce its size somehow. I use a free downloadable program called Irfanview from
www.irfanview.com, but there are other ways - you can do it in Microsoft Paint or other kinds of graphic programs, or depending on your email package you can email the picture to yourself and the email package will automatically resize the picture for you.
Once you find the picture or pictures you want to include, click on the Upload button and wait until you see the picture's filename appear in the Current Attachments box. Then, you can close that new window and submit your post.