Actually there are couple of threads similar to this one that was started at
http://webdesignerforum.co.uk All you basically need to do is, first think of what you want the overall site to look. I know you have a template, so in your case, you will need to know how you want to manipulate the layout so that it suits you. You can use softwares such as Programmers Note Pad 2 (a freeware) and code your site according to your liking, you can also use premium softwares such as DreamWeaver or FrontPage and edit it in a live preview kinda situation. Some hosts, such as those that uses cPanel, already have such option to edit templates in action, so they are easier and helpful. If you use zymic download the software and edit it.
If I am correct, the template from the link you provided are basically templates created either by TemplateMonster or 4Templates Inc. Therefore they are professional designs. Hopefully you did not download a flash template because it will be a pain to work with those and you will need some experience in handling action scripts.
I would say read up on the threads at the link I provided above and
http://htmldog.com/guides/htmlbeginner/ I would also review the basics of CSS for Beginners.
And most importantly, express yourself through your work and have fun!!!