Hi Lottie,
If you want your own website, you can either create your own using a template site (rare-escorts and moonfruit are popular), or you can pay a designer to sort something out for you. Since you don't really know what you're doing, it would be worth going with a professional designer if you have the money and are confident that you'll be happy in the business. Girls who start with free sites usually get a professional one when they can.
There's a discussion about building your own site
here, and some recommendations for web designers
here.
In the meantime, a profile on adultwork.com is a good place to start and a lot of girls get enough work from there that they never advertise anywhere else. Most of the profiles have a low-rent style, but don't feel that you need to conform to that to get work. Make sure you're clued up about the practical aspects of escorting, especially safety, before you get started. Some people try to take advantage of new girls, especially on AW.