The principals are the same for Imageshack or other pic hosting sites.
Start your new thread or post on exisiting thread.
Select your uploaded pic from photobucket. Once you've done that put the mouse pointer on the pic and you will get a window pop up under the pic you selected. Move your mouse to the window and click on the Direct Link "copied" will replace the url after about a second it will go back to the url. You now have the file location copied to your clipboard.
Below is what you will see when the link is being copied.
Once the file is copied to the clipboard it will go back to something similar to this.
Go back to XDTalk thread and click on the yellow "landscape" icon.
A link window will pop up. Click in the link box.
Right click your mouse button and select past. The link URL will show up.
Click OK and the picture will show up in you post.
If you need instructions for uploading pics to photobucket post and I'll add them here.