Action doesn’t just mean fights and chases, it means whatever physical acts a character has to carry out to achieve their ends. Describing action in a screenplay can be difficult for those unversed in the technique.
For one thing, everything must be stated in the present tense. But the most important element that the writer must encompass that his description must be written as if he is the camera. He must see in his mind’s eye, and detail on the page, whatever is important to the story.
So, he can pan, zoom and go for a close up to make his point, without intruding on the director’s domain.
Elaborate description is not required, it is the action which is important.
For someone switching from pure prose to screenwriting this may feel unnatural, but remember to see only what the camera sees and detail only that which is vital.
For all that film is seen in terms of the silver screen and blockbusters the writer must approach it with the lightest of brush strokes. Take time into account, the threading of a needle demands as many words as a huge explosion if they are to take up equal screentime.