The Radar screen can be accessed in a number of ways. Only while there are completed Radar tasks waiting to be "popped" is there an icon in the lower left hand corner of the screen while inside the base.

Radar tasks are short activities that provide generous rewards for completing. You get a specified number of tasks every 6 hours which expire after eight hours if not done. In addition, these tasks can accumulate up to a certain number before becoming full, at which point the 6 hour timer stops. Because the Alliance Duel has three days in which Radar tasks provide a lot of points, it is advised that you accumulate these tasks on the days before so you are one less than full at reset. Radar Tasks score extra points on days 1, 3, and 5 of Alliance Duel.

Otherwise, there is a building within your base that will take you there,

and when in world view the Radar icon is always visible in the lower left hand corner.

Tapping any of the above three items will take you to the Radar screen. Pictured below is a full field of completed Radar tasks. The red dot in the upper right of each task icon shows that it is complete. Tapping a completed task "pops" it, a reward is collected, and points are scored if on an appropriate Alliance Duel day.

The items at the top of this screen should be fully understood to maximize your effectiveness in using Radar tasks. Depending on what Radar level you are at the numbers will be different.