how to can i make the character as long he enter the box collider it wiil print "hello" (blueprint)

Development Getting Started & Setup
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1

so basically i made an actor which contain only a box collider ,and what i want is that as long the character stay in the box it will print “hello” and if he leave the box it will stop printing “hello”.

2

You could have tick disabled on the BoxColliderActor as default, then:
On Box’s BeginOverlap → Enable Tick
On Box’s EndOverlap → Disable Tick

On Tick → print string (“Hello”)