Once you have decided your niche and bought your domain, you now need to setup a host. The host is where your web site “physically” sits. I would recommend a host where you can do a one-click install of the software that you’re going to run your website with. For most of you this will be Wordpress. If you aren’t using Wordpress, you should definitely ask yourself why you aren’t using Wordpress. This is the easiest and probably most widely used web platform on the internet. It makes everything easy.
Setup your host by adding the domain to your host account. You will need to point your domain to your host (for example, if you bought your domain with GoDaddy, login to GoDaddy and go to edit nameservers). After doing that, install Wordpress to that domain on your host.
One of the easier hosts to work with if you’re new at this game is Dreamhost. Their reliability and performance isn’t as good as other hosts, but it will get the job done for a new site. You can always change hosts later on. Dreamhost is also cheap.