DV360 leverages the Advertiser level "Location List" in order to set the targeting on the Line Item
Setup Time: ~2 minutes
At the Advertiser Level
Left Menu>Resources>Locations Lists.
Give your location list a name an select the Proximity Targeting option. Once you've uploaded your latitude longitudes, click the Validate Button
Go to the Line Item and under Add Targeting>Geography
In the Geography selector click the Radius option and seach for your location list.
Goldfish Ads will provide you with the optimal Radius to use with the targeting file. This radius will maximise the coverage of the audience while minimizing waste.
Finish by clicking "Apply"