Start by signing in to GitBook. If you used the previous version of GitBook and already have an account, you can use the same credentials to login to the new version. If you don't have an account yet, sign up and create a new account.
You need an organization to create a space. If you don't have one already, you will be able to create one and create your first space in the process.
Follow the steps and you will be brought to your newly created space.