How do I tighten the timing chain on my car.

The timing chain tensioner does not appear to be adjustable and is hydraulically tensioned or static as there are not any adjustements mentioned in installation instructions.
There are 2 timing chains, inner and outer, and the inner only has a chain guide. If you have never done the timing chain or if it is over 70,000 miles since both have been replaced it is likely the chains and/or gears are in need of replacement.
I included a diagram of timing chain components so you could see how it is set up.