2000 Chevy Blazer First time self repair job

Other Category problem
2000 Chevy Blazer 6 cyl Wheel Drive Type unknown Automatic 11700 miles
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How do I flush the radiator (system?). I discovered a leak a few days ago, just above the middle of the front axle (where that big triangle shaped housing is) and then my engine started to overheat this morning.

Thanks,

Lorena