Keeping my Fish alive in a new tank.

Question
Hello Fish expert :) I am brand new to this whole aquarium upkeep but i am very interested in learning on how to do it right and keep my great fish alive. I first went to 3 different fish shops and got told three different things. From everything i have read online i'm sure i'm doing something wrong and don't want my fish to die. So here is what i have done so far. Last week i bought a 20g aquarium. I hooked up the air pump with the filter and put the stress coat drops and the other stress zyme drops into the water and let it sit for 48 hours. I then purchased 3 different kind of fish and placed them in the aquarium. The water started to get a bit foggy so i know it wasn't clean. I then went to a different fish shop and they told me to purchase a bigger filter and it would clear it up right away if i did a water exchange. So yesterday i did a 5 gallon water exchange and put some more stress and zyme drops in the water. It cleared up a tiny bit. Well my lil sister was extra fascinated by the new tank and purchased two more fish to add to the tank. I placed them in this morning. but from what i am reading that was a bad idea. Now i have 5 fish in the tank the aquarium was just purchased on Tuesday and the water is still not clear. What can i do to save my fish and also get the water clear? Please help!!! thank you so much.

Answer
Kris,  Before we can get an answer I need to know a couple of things, I need to know what kind of fish you put in there ...tropical , goldfish etc. Explain to me exactly what kind of mechanical filtration you are using .(describe your filter or give me the name of the brand) ,Tina OH and how long has this tank been up?