You could use a transformer that can be installed outdoors (example) or a wet-rated transformer that must be protected (example). Use outdoor cable of the appropriate gauge (example) between the transformer and lights with the appropriate connectors.

Follow dark-sky guidelines for outdoor lighting:

"...lighting should

• Only be on when needed
• Only light the area that needs it
• Be no brighter than necessary
• Minimize blue light emissions
• Eliminate upward-directed light"