-> You have bought your domain name from a domain service provider.
-> You have bought hosting for that domain name you have registered.
-> You have installed WordPress.
WordPress comes with a default theme based on the installation version. But that is hardly good to look at. If you are going to run a website/blog which you want people to check out and come back for more, you are going to have to make your blog as neat and as presentable as possible. This is where having a premium paid theme comes in. Mistake me not, there are some good looking free themes available for WordPress. But they come with their own limits. With a premium theme, you can have many customization options. Also, you can definitely find one suitable exactly for
the purposes of your website/blog.
There are a few really good, premium theme providers that I know of. I personally use GENESIS themes for my blog. It’s a combination of Genesis Framework + Child Theme that I had to install with WordPress in order to get it up and running. I won’t say that any theme will be up and running with just installation. It will be up and running, but it will need improvements, customization from your side which only you can do – either by yourself or with the help of someone who knows his/her way around this kind of stuff.
The following are some of the theme providers you can look into.
When you buy a theme, they will provide you a zip file which you can upload into the themes section of your WordPress dashboard and then you can take it from there and customize it according to your needs. In my view, if you are a non-programmer, Genesis themes are the easiest to use. If you are a programmer and you like building stuff according to your needs, go with Thesis themes. If you are going to choose the other theme providers, do your research before you go with them.
Following are some of the resources you could use to do your research to read about these premium themes & theme providers.