Esy_777,
First, welcome! And welcome to the world of SW tanks.
There are a few different answers to your question, but I'll try to keep it as simple as possible.
First answer - none. Not for a while, anyway. You don't want to add any fish until the tank has completed the ammonia cycle (ammonia --> nitrite --> nitrate --- nothing). Usually, the cycle is started by adding some sort of dieing /decaying matter, such as uncured live rock, a raw grocery store shrimp, etc.
Once the tank has cycled, you want to add one, possibly 2 small fish at a time. And then, wait at least 2-3 weeks before another fish addition.
As far as "total" (eventual) fish go, a lot depends on the type of filtration, the type of fish, and the type of tank (fish only, reef, etc.). The usual *guideline* is one inch of fully grown fish (not counting the tail) for every 5g of water.
So .... in a 33g tank, you could have approximately 7 inches of fish max, or 3-4 small fish.
Hope this helps!