OK, a marquee (as they're called):
<marquee behavior=scroll direction=right width=50% bgcolor=black>
insert text here</marquee>[code:1]<marquee behavior=scroll direction=right width=50% bgcolor=black>
insert text here</marquee>[/code:1]
:alien:
I'll break that down a bit:
<marquee
The start of the description of the marquee itself (the 'open marquee' tag).
behavior=scroll
What you want the marquee to do. The options are:
alternate <marquee behavior=alternate width=50% bgcolor="#FFFFFF">like this</marquee>
scroll <marquee behavior=scroll width=50% bgcolor="#FFFFFF">like this</marquee>
slide (you may have to refresh to see this) <marquee behavior=slide width=50% bgcolor="#FFFFFF">like this</marquee>
direction=right
Which direction you want it to go. 'right' is left-to-right, 'left' is right-to-left.
width=50%
How wide you want it to be. This can be a percentage of the page width (as above), or just a size in pixels (with no '%' ).
>
The end of the 'open marquee' tag.
bgcolor=black
What color you want the background to be. Most color names will do, or a 6 hex-digit color code (eg #007F7F is turquoise).
What color you want the text to be. This must be one of the color names recognised by Ikonboard.
insert text here
Obvious. 
</marquee>
Closing the tags I opened earlier.
PS: I'd like you to work out the specifics on your own. Think of it as a kind of test of your worthiness. :buttrock: