How do I practice a specific opening with Lichess?

How do I practice a specific opening with Lichess?
For example, I want to learn the King's Indian defence.

How can I get "the machine" to cooperate by playing the right moves?

I want to do 1. d4 Nf6 2. c4 g6 but it just keeps opting for other moves. Do I have to keep aborting games until the right combo appears?

Once it appears (still waiting) it likely won't happen again for ages.

http://en.lichess.org/editor
you can set up any position you want, also you can choose openings on the right, then click "continue from here" and click on "vs_machine"

Ah. Excellent.
Was starting to lose patience,

You could create a thematic tournament with your preferred opening. All the games will start with that one.