This is a bit more 'complicated' so bear with me. For starters, hotlinking = no-no. Hotlinking is when you directly link the source of the image. It uses the bandwidth of the owner of the site, and it can cause problems for some sites, because they are allowed to use so much bandwidth a month. To combat that, some of those site owners will change the link of the picture, so whatever image you've hotlinked now comes up as a red 'x'.
Now, onto linking pictures.
Easiest way to do it is to save the picture to your desktop. Right-click on the picture (if you use Internet Explorer, I don't remember the option) but in FireFox, it's "Save Image As". Save the picture to your desktop. Now, go to a picture hosting site, like
photobucket (you have to register - this is good if you plan on hosting multiple pictures), or
imageshack, which is good if you're linking one picture. There are others, but I won't list them all.
From there, you click 'browse', find the image you want to show, and upload it. You'll be given a link, which will be something like
http://www.imagehostsite.com/picturename.jpg or whatever.
Now, if you're linking on a forum, you need the IMG tags. [IMG*] picture - link - here [/IMG*] (you have to take the asterisks out). Most forums have a little artsy picture that you click on and just post the picture link, and it'll insert the tags for you.
If you're linking on a website or blog, you have to use the HTML tag, which is
.
Hope I helped. If I haven't, then ... you're on you're own.