Slitherine

Okay this might sound noobish question... How can I use my fresh new
Airborne division. Do I need to keep it at a city or near airplanes? Do I have
to load it to planes?

Thanks

Page 94 of manual:

-adj to city or friendly air
-70+ eficiency
-fair
-not adj to enemy

then, when you select it, the para symbols will appear where it can drop