Use the Go Advanced button at the bottom of the posting editor. On the advanced page you will see a Manage Attachments button just below the posting editor. Clicking it will open a new Manage Attachments page without closing the posting window (or new tab if you are using a tab activated browser).
On the Manage Attachements page there will be four input boxes, each with a Browse button on the right allowing you to add up to four pictures per post. Click a Browse button and (assuming you are using windows, Mac and Linux have a different display) you will see a popup directory displaying files somewhere on your hard drive (where depends upon the last use).
Use the Look In drop down to navigate to the directory that contains your photos. The third icon on the top that looks like a Monopoly card will let you see the directory in several formats, including thumbnails and I find this the easiest to select the pictures I want. Click on one picture that you want to upload, then on the Open button (or just double click the picture). This will close the popup and you will see an the name of your file displayed in the input box.
Repeat the process up to 4 times then click the Upload button. When all the photos are uploaded, you may close the Manage Attachments window and return to the posting editor (you can return to the posting editor at any time even if you leave the Manage Attachements window open).
If you were successful you will see the pictures listed above the Manage Attachments button. Finish your post and click Submit Reply.
Let me know how I did on the instructions and I will save them off/modify them for others.