To create a website login to your office 365 login page
. And chose your Office 365 version as per your requirement. Here we will do with Office 365 Enterprise trial version.
This will open the registration page where you need to set up your account. once you create your account this will take to the home page.
Then click on "Site" on the top as shown in the figure below:
Then in the home page click on + new site button as shown in the figure below:
Then it will open the Start a new site dialog box. There enter the site name and click on Create as shown in the figure below:
This will create the site.