If you're using photobucket, follow these steps.
1) After you've uploaded your pic, hover your mouse over it.
2) A drop down menu will appear, with the following options
Email and IM
Direct Link
HTML Code
IMG code.
3) Left click in the box next to 'IMG code'. This should highlight it.
4) Keep your mouse pointer there and right click, and chose 'copy' from the options.
5) Come back onto NESA and right click in the 'New Post' box, then chose 'paste' from the options.