There's a good diagram on this link. You'll see it posted on the forum as reference a lot.
The bypass valve is usually located very close to your HW tank on the inside of your TT.
To pump in anti-freeze, there is usually a clear hose located on one side of your water pump.
Not all TT's come with the hose already installed, but many do.
My pump is located under the kitchen sink, but they can be anywhere. If you have trouble finding it, turn on the pump, open a valve and follow the noise.
Here's a decent video for pumping in the anti-freeze and accessing the bypass valves. May want to fast forward to 2:30.