Tough and easy question. As Jeffdengr says, Master Lin is not explicit about How to open the channels. However, he talks about opening channels all through the course material. Things like, "10% of the people's channels open as soon as I say all of your channels are open". This would be a good time to have Confidence that they are open when you direct you mind there. He also says, "When you relax your channels automatically open". So relaxing deeply will open them automatically. He also says, "Where the mind goes the energy follows", so if you see yourself with open channels, think your channels are open, believe they are open, then they will be open.
I do it several ways, but probably (I don't always consciously go here) physically relax. I have a few visualizations and feelings I set and work to create. They are based on times when I felt very open and filled with energy. But don't get hung-up about re-creating these things, set them apply and trust that the universe is providing the experience that is perfect for you.
You are perfection.
Iam2