To start buying or selling stocks, you should open an account with a brokerage house such as Scottrade or TD Ameritrade. If you live in the U.S., they are required to have you fill out some forms. You must put money into your account before you can begin to order trades.
They will give you a password to access their trading site online. You select the stock you wish to own and place your order with the brokerage either by phone or online electronically. During the business day, the brokerage makes the trade for you, usually within seconds. They charge you a fee for each trade, typically 6 to 10 dollars to buy or sell a “lot” of 100 shares.
The shares that you buy are kept on file at the brokerage. Many companies no longer issue certificates for shares but keep track electronically.
When and if your company issues a dividend, the money goes directly to your account.
You can get more information at their websites.
At Share City
Stock Brokerage Houses are allowed to trade on the market(buy and sell shares). You need to open an account with one that will allow you to buy shares. Keep in mind that each brokerage house has their own rules, like minimums for opening an account, fees for each transaction (buying or selling), etc. I believe E Trade has one of the lowest minimums for setting up an account, but do your homework.
You can open an account with any registered broker/dealer, deposit funds into the account and you can be ready to invest/trade.
You should visit the sites of several firms to see what site best fits your needs. While visiting the sites you should check out the company's fees & charges, their services and how comfortable you feel using the site.
Through a broker
Call a broker or use TDAmeritrade