1. Add your domain to your Fabrik site
Go to Settings > Domains and link your domain.
Make sure both the root (non-www) and www versions of your domain are added. This way it doesn't matter which URL someone enters, they'll still end up at your Fabrik site.
2. Choose your primary domain
Every Fabrik website has a primary domain/URL. If someone navigates to a non-primary domain we redirect them to your primary domain. What you choose is up to you - personally we favour the non-www version (e.g. yourdomain.com) because it is shorter and looks nicer in the address bar.