Same as with almost any other reactor: Steam running through turbines. The high temperatures are important to sustain the fusion process. The goal is that it practically self sustains itself while we just continue to feed it with hydrogen.

I think the current designs would all use radiation heat, which means infrared etc light hitting the reactor walls and a coolant (water) running through them to generate steam, and then it's the good old turbine to electricity process... Light emitted from a plasma that hot isn't that hot itself / wouldn't heat reactor walls to the same temps.

Steam turbines aren't the only way, certain fuel cycles permit direct energy conversion: https://en.m.wikipedia.org/wiki/Direct_energy_conversion

Whey do you mean? Everything is just stream!