You might want to pull a search on
SEO, and read the marketing & business sections for more advise on websites, sales, managing your business, etc...
You stated your domain is registered - do you have a hosting provider? If not there have been numerous threads on that, some free, some that charge - I prefer to pay for the hosting as the only "Ads" I want on my site are mine. Is it being hosted on an IIS or Linux box --- That dramatically changes what you can use for contact forms, etc...
You can create HTML code using any numerous software programs including notepad. I prefer using Microsoft Expression for my web site. Just starting out - sure you can do it by yourself, as your site grows, etc... you generally will find it cheaper to go with a professional, which is where mine is going shortly.