ArcGIS Pro is dependent on ArcGIS Online, so in order to have ArcGIS Pro running on your desktop, you must have an ArcGIS Online account. You can either download a trial version of ArcGIS Pro or you can purchase the personal ESRI yearly license, which should also provide you with access to Pro. Regardless of how you intend to install and use ArcGIS Pro, the procedure should be standard across the board. As I said earlier, you must have an ArcGIS Online account. When you sign in to ArcGIS Online as the administrator, you should be able to click on My Organization and provide authorization for each named user to use ArcGIS Pro. If you are the administrator and you don't see My Organization in your ArcGIS Online account, you might need to contact ESRI to make sure it is set correctly for your license level.
Before working in the ArcGIS Pro...