When I use pictures in this forum here is what I do.
1. Take a picture of what I want to upload with my old 4 MegaPix Kodak camera. Some use a scanner. Use whatever you feel comfortable with.
2. Upload the pictures to a folder on my desktop.
3. I use a freeware online program to edit most photos. Do a search in your favorite search engine for Paint.NET. Very simple to use. Or also do a search for PhotoScape. PhotoScape is another great free downloadable photo editing software. PhotoScape also allows for round cropping of pictures which is great for coins.
4. Use the photo editor of your choice to make any adjustments and crops that you desire.
5. Use your photo editor to re-size your photos as desired. For most websites 500x500 is the largest aloud. Some websites also regulate the allowable size of pictures by the pictures file size. Point to the file with your mouse cursor and right click on the files icon. Click on properties to see how large the file is. You may need to re-save it at a lower quality.
6. After you save your edited photo (I usually save it in the same folder on my desktop as where I saved the original (Be sure to save it as a JPeg file)). I upload them to photobucket.com (free web storage of photos that is free to use for a basic account).
7. When the pictures are uploaded to photobucket.com you can hover your mouse cursor over the picture you want to upload. When the mouse is over the picture it will open a window like the one in the red box here:

8. In the box...choose the last option "IMG Code" (shown in the red box). Hover your mouse cursor over the area shown until for a few seconds then click the left button on your mouse. The word "copied" will appear for just a few seconds. This will copy a direct link to your picture.

9. All you have to do is when your are creating a post in the forum and you want to put the picture in is copy the direct link from photobucket for the picture you want (see lines 7 & 8) and then paste it in the body of your post where you want it to be. Its as easy as that. Well...It will be once you get the hang of it.
Good Luck.