sharing icloud storage between iphone x and mac

iCloud storage is linked to the Apple ID that you use for iCloud, not to a specific device. If both your iPhone and Mac are using the same Apple ID for iCloud, the iCloud storage space should be available to both devices. If you turn on desired sync settings on the iPhone at Settings > [username] > iCloud > (e.g., iCloud Photos, Contacts, Notes, etc) and turn on the similar settings on your Mac at Apple menu > System Preferences > Apple ID > iCloud, the data should automatically sync between the devices.

Also see: Set up and use iCloud Photos - Apple Support and iCloud Drive FAQ - Apple Support