So let me explain how this work, service Search for An Enemy will search through all enemy pawn and pick the nearest one each 2 second, it AI have target, it will set the value Enemy in Blackboard, then the service Shoot An Enemy will fire at Enemy for each 0.5s. So if you want he just stand there just cut the link to HasEnemy. That HasEnemy selector only run if Enemy is set and it will run task sequence which it is find a nearest point and moving near to the Enemy.
You can change this with what you want to do, like move to some point near the enemy first then standing there and shoot, this need some additional work though, but when you understand how think work it should be easy.