I think the best place to start is by signing up to photobucket, it is a free photo hosting site. You upload your pictures to it and from there can post them on the forum.
This is the link
http://photobucket.comWhen you have signed up you will see the option to browse and by clicking on there you can open the photo album on your PC and choose the pictures to upload. I resize mine before but you can re-size them on photobucket too.
When you have done that you just click the image link, bottom choice and it will automatically copy the picture.
Then you right click on your thread and the picture link will be added.
If you have any problems you can pm me and I will help you, or maybe someone else will explain it better. You can ask one of the mods, they are used to helping with pics and may know an easier way.