Pocair, you should get some books. One book that helped me a lot is a book called Your First Marine Aquarium: A complete pet owners manual.Saltwater aquariums are sometimes, and sometimes not hard to manage. For instince, I check all my tank's ammonia, nitrate, nitrite, ph, calcium, alkalinity, strontium, iodine, phrosphate, and copper every two days to make sure the enviorment in my tank is stable. Keep a notepad by your aquarium so if anything out of the ordinary is going on inside your aquarium, you can wright it down. I also watch my fish regular to look for any odd things such as gulping, paleness, etc. Use these signs as a signal to you that someting could be wrong in your aqurium, filter, etc.
I made a little table for you so that you know what is normal in the water in your aquarium.
ph: 8.15-8.6
alkalinity: 2.0-5.0 meg/L
Ammonia: 0-0
Nitrite: 0-0
Nitrate: <20 mg/L (ion)
Phosphate: < 0.05 mg/L
Strontium: 8.0 mg/L
Iodide: 0.6 mg/L
Dissolved oxygen: >6.90 mg/L
Since you have a five gallon aquarium, you have limited choices to fish. Since your new to saltwater fish, stick with damsels and clownfish. They are very hardy and should last for a long time. Also get some type of small algea eater for every gallon to keep your tank extra clean.
Heres a little summary a made for you about the fish:
Clownfishes and Damselfishes (Pomacecentriae)
Clownfish are damselfish that live in association with certain species of anemonies in the ocean, but may be kept without them in an aquarium. Most popular is the common clownfish or false percula. Other good choices of clowns are are clarks anemonie fish or clarkii clownfish, the tomatoe clownfish, and the maroon clownfish.
Typicaly, a group of clownfish consists of a dominate female, a smaller less dominate male, and several juviniles. In order to be like this group, clownfish are capible of changing --- as they mature. One problem with clownfish is keeping different species in one aquarium. As the clownfish mature, they become more aggresive and will fishting. It is best to keep only one species of clownfish in your aqurium.
Like i said, Damselfish are one o the most hardy fish in aquria. Although the fact that they are genarally aggresive, some aren't. The best choice would be they orange tiled damsel.
If you want an anemonie, you better be prepaired. The lighting for an anemonie costs a lot. Laso it would be better if you already have expierience with them. If you don't want an anemonie, you can get a feather duster. They don't require a lot of work.
When adding the live rock, stack them so fish can swim through it like in the example (below). I did it quickly in paint so its not that good.
When you become more expirienced, you maybe should get a bigger tank; 20 gallons max. Then you can expand what you buy. Hope this helps!
P.S.: Can you get a picture of your tank here?
Salty:happyfish