I agree with the previous posts from both Logansmomma & HN1.
I would suggest, if you can to trade in your 5.5g for at least a 10g. This way, the tank will be a lil' more forgiving for water parameter swings & also temp swings. Both kits go for approx the same price.
As for cycling, like HN1 said, most of us have all started out not knowing much about fish, and all ended up on forums like this one to learn why our lil' cute aquafriends died after a week.
Running the tank overnight will do nothing but circulate water.
You want to learn about the Nitrogen Cycle. This same cycle applies to earth and our lifestyle but this is also very important in your aquarium to ensure your fishies are not living in their own wastes.
In a short and simple desc:
Fish waste & decaying un-eatened food are both sources of Ammonia.
Ammonia is extremely toxic to fish, and will kill a fish at levels of 0.5PPM +. The Ammonia is turned into NitrItes, which is also extremely toxic at levels of 0.5PPM+. The Nitrogen Cycle is completed by the Toxic NitriTes being converted (by the good bio bacterias) into NitrAtes, which are less toxic and safe for levels +-20PPM.
Once this cycle is completed, your fish can then be added, and with regular weekly maintenance (35-50% partial water changes & dechlor + Filter cleaning) you will be able to enjoy your new hobby, and less likely having to deal with treating for parasites or deal with fish deaths.
If you search the forum using the search bar, you will learn how to start a cycle using raw shrimp or Pure household Ammonia (unscented).
Enjoy, and good luck
Welcome to AA