Need Help with my car coolant.?

I got buick regal 1999 model and since last week i was getting a sign for low coolant and use to go away when i use to drive. So I thought to add some coolant. I added some peak 50/50 long life coolant in my car and the light still exist. Firstable I didnt know about cars so I filled it up way above hot zone. Second thing today i was reading my car's owner manuel and I noticed they say use Dex-Cool (Silicate free) or it will avoid my car warrenty, which im not worried about cause i dont have any lol. So my question was should I leave it the way it is or do something about it. Will it harm my engine? I just added it day before yesterday and barely drove my car.