About Activity Diagram.

sheritom: 1.put the octopus card onto the card reader.
2.display the remaining amount on the screen.

Hi,
I am having an assignment and I dont know how to draw these statement in Activity Diagram.
i dont know how to draw when the activity involve displaying.
should i add item " screen(or Interface)" in the swimlane??
if not, how to do it?
please tell me.

I will appreciate your kindness.
thank you.