I cheat. Rather than memorize the simple codes, I just pasted them to the notes section in the Home screen. You can paste your own URL over the one there, copy the whole thing, and voila.
If you're not friendly with html, know that you can remove parts of the code to simplify it (like the alt names and border=0). However, CB doesn't auto-adjust massive pics, so it's best to know this: if the image is massive, try replacing width & and height codes with simply Width="70%" or any other proper percentage.
LINK <a href="
http://www.url.com">title</a>
IMAGE <img src="
http://www.url.com" width="100" height="100" alt="title" />
IMAGE IS LINK <a href="
http://www.url.com/" target="_blank"><img src="
http://www.url.com" border="0" alt="title"></a>
VIDEO <youtube> </youtube>