To create a new site collection, click on the New button and choose Private Site Collection.
If your tenant has licenses for projects, you will also see an option for creating a new project site collection. If your tenant was created before 31 January 2017, you may also have the option of creating a new public site collection. Do not use this option. Microsoft is phasing out the use of this type of site collection. If you want/need a public facing site, we suggest using another medium, such as WordPress or Wix. You can get 50% off your first year of a Wix or GoDaddy website by initiating it through your Office 365 admin center under Resources | Public Website.
After clicking the Private Site Collection option, ...