You know the connections menu? When you select a bomb a "arrow pointing right" should pop up,that gives you the. Rotations menu,but right above the rotation button there should be a cable connection to an outlet icon, there you found the connections menu

Put the parachute where you want it to be,it will not attach,after that,select the parachute and in the connections menu go: "add connection"

Select the parachute connection point,then select the bomb, select the connection point( little piramid)

Voila,u got it! However MAKE SURE THE BOMB IS ATTACHED TO THE AIRCRAFT FIRST

Or else it will fall off

Hope I helped! Goodbye!