Drain your system. I would say find a way to dry the system out as best as possible since with Evans you want absolutely no water. It needs to have less then 3% water in the system ideal to have 0% water in coolant system. Buy the prep fluid which is $33 dollars. run that through then add the Evans coolant which I beleive is 43 dollars. I will have a trusted mechanic friend do it for me.
I plan to use a wet vac first and a small tube to evacuate as much as possible.
(Home Depot offers a "Bucket Head" wet vacuum that fits on one of their orange buckets for twenty bucks plus the cost of the Orange bucket for three something for the bucket, if you need a cheap wet vac).
I will drain the lower radiator hose first and replace the crimp on clamp with a T-Bar clamp which is of a much higher quality and strength than the typical screw clamp. I think I recall an engine being ruined when the screw clamp they used on the lower radiator hose failed,
and they lost all coolant.