Nikkkk, in order to start you have to open a bokerage account.
One of the reputed ones that I know of is Vanguard.  www.vanguard.com
A lot of my friends recommend it because of their low fees.
You gotta go on to their website and open an account.

Once you open an account, you can transfer your money in and start buying stocks and exchanging traded funds.
For most Vanguard funds, you need $3000 to start. If I am not wrong, the Vanguard Star fund is the only one that requires an initial investment of $1000. For beginners, I think it is best to start off with mutual funds because it is diversified and professionally managed.

You also gotta think about how much risk you are willing to take. If you don't want much risk, there are always options like Coca Cola, Walmart, etc. With these, you are not gonna be doubling your money anytime soon but there are chances of growing your investment without losing much.

I dont really know how to explain this properly but once you start you will be able to grasp certain things. Good luck.