Weapon Platforms @ Warp Point - Newbie Question

[tbontob]

Up till now, I've been playing my games with attack ships to deal with assaults on my systems.

That can be expensive because of the maintenance costs.

Then I came upon a thread discussing the relative merits of mines, weapon platforms and satellites at warp points.

So, I started a new game, built some small weapon platforms, loaded them into a transport, went to a warp point and........couldn't unload the platforms!

What did I do wrong?