You can use them in e-mails yes, but instead of linking the image in the e-mail like you would with forums, you actually save the image to your computer.
So right click on the image, select 'Save picture as'. Save the image to anywhere on your computer. Now to use it in an e-mail just open Outlook Express start a New Message, select 'Insert' from the top of the New Message window and then pick 'Picture'. A screen will pop up and you locate the image you want to use with that. Then when you have the image you want to use, double click on it and it will appear in your new e-mail. Now just to make sure the image appears on someone elses computer you should always attach the same image, so in fact you're sending it twice. So select 'attach' from the 'New Message' window, usually a paperclip picture, select the same image you picked before and click okay.
Now type your e-mail and send it to whoever you want to, they should be able to see the picture.