You simply deposit funds in an account and use any of your choice of online brokers such as Ameritrade (the one I currently use), e-trade, scottrade, Schwab, etc...
You buy and sell at the click of the mouse on most stocks and bonds.
If you want any additional information, simply put "online brokers" into your browser search window and it should bring you up a list of brokers to choose from. If you want any other information contact me and i'll be glad to help you in any way I can.
Most online brokers require a minimum of around $2,000 to start an account, but I think Ameritrade and some others will allow an account to start with as little as $500. There is great potential for making money on it so I recommend you get into it as soon as you can
Thanks for the post.