Well, assuming you know how to use imageshack or photobucket or some other site like that, go here and pick a banner to use.
MTW Banners
And then you can try using this html code.
HTML Code:
<a href="http://www.MortysTwistedWorld.com" target="_blank"> <img src="PUT IMAGESHACK URL HERE"> </a>
Place the URL of your imageshack hosted file BETWEEN the " " and it should work like a charm. This code will make clicking the banner a link to MTW.