Create a free account on a host site, such as Photobucket
. Upload your pics to it. Photobucket will automatically downsize the pic to fit on the forum.
After it has finished uploading, click on the "IMG" box next to the pic and the contents will automatically be pasted into your clipboard. Then just paste that into a post on here. Click on the "Preview" button to see that it worked before you finish posting the message.
Hint: If you're going to be using Photobucket for a lot of pics, start out by creating different albums for different themes - hobbies, cars, Jeep, sports, food, etc. It makes things much easier to find years later.