Go to the BP_SmartAIComponent and create a new Bool variable called In Attack then copy the images below by adding the highlighted nodes. Locations at the tops of the screenshots.

Next create a new custom event in the event graph and call it FrequencyTimer then add a Float input called Time. Then create another custom event called StartTimer. Then copy the image below, location shown at the top of the screenshot.

Next go to the locations shown below and add the highlighted nodes, locations at the tops of the screenshots.