The (simple) procedure should be on the cap/skirt on the bleed-bolt. Be sure the center hole in the bolt isn't blocked.
The detailed procedure from cold engine when the system has been opened, is to loosen the bolt, fill the radiator until coolant flows out around the bolt (pump the top hose to be sure no large air pockets are present), install the radiator cap, tighten the bolt, be sure the overflow tube to the coolant expansion tank isn't blocked, add coolant to the HOT line and drive. If the system is operating properly, the next time the engine cools down overnite, the level should be close to COLD. Be sure to use s straight !6# cap, not one that works over a range, say 13 ~ 16. Drive it around for a couple days and pay attention to the level in the tank. Only add if below COLD overnite. Resist the urge to remove the cap and peek into the radiator.
After a few days and once you're confident the cooling system has stabilized, if you still see an intermittent light you can move to other checks, etc.
What you can do now is to check the connector at the ECT to be sure it's clean and fully seated - do the same for the ground connection for the harness to the header panel in front of the battery.