It is also a good idea to call the company and see if they will send you an investors package. If the company is private, you're out of luck. Privately owned companies don't offer shares on the stock exchange. To invest in the stock exchange you must go through a broker. There are many brokerage firms for you to choose from or you can invest through any bank.
Many banks now offer investing services.
It is advisable for you to meet with a broker to find out the details on commissions. If everything goes all right you should now have stocks in a company, meaning that you own a certain percentage of that company. Hopefully the stocks will rise in price. If the stock rises in price you can sell the stock and make a profit. To sell your stocks simply call your broker and ask them to sell your shares in the company you chose.