You need a leader or a scout. Select the leader, there will be a small button that looks like an explosion above the selected units window. Click that button and it will show on the map where you can attempt to target. Click on a highlighted hex and the game will roll to see if the spotting round scatters. If it scatters out of LoS, it done. If it scatters but stays in LoS you get a chance to move it one hex. If it doesn’t scatter the strike will then happen.