From DCS World Wiki - Hoggitworld.com

LotATC is a 3rd party application for DCS World, written by DArt, that displays the active map of a server in a more friendly and accurate view to simulate the radar screen of an Air Intercept Controller or other radar operator. It provides tools for persistent BRAA (Bearing Range Altitude Azimuth) and for controlling precision approaches to all the airfields in the existing DCS World terrains. The application will also interface with Universe Radio to simulate Transponder and IFF functionality.

LotATC Client

From their site:

“LotAtc is a client + server software witch is connected with DCS World Simulator and provide users to get an ATC/CGI view of the battle. Play the role of a tactical or air traffic controller and provide help to human pilots so that they better accomplish their missions, by radioing them a picture or guidance instructions!”

The official LotATC website has detailed, step-by-step, installation instructions for both the Client and Server versions of the application.

They have a Discord server for users to collaborate and discuss the application.

The official DCS Forums also have a post for the application.