How do you place drop zones?

There are 4 steps to place a drop zone:

#1.On the top right corner of the screen you will see a blue circle parachute button called the "Reinforcement Menu" <<click it)

#2 Pick what units you want

#3 Click the drop zone button (its a rectangle); you can only drop your units where there are the yellow lines.

#4Click the deploy units button (its a circle button at the right-bottom of page.)

Hope that helps you out.

Thats what I've been trying to do but the reinforcement button is unclickable for some reason.

Does this happen in online game play or offline or both???

I'm doing a LAN game but with just me and the computer playing, no other real people players.