You should now be able to see your Expert Advisor in the "Navigator" window in the bottom left hand corner of your Metatrader 4 platform, shown below.
Select the new EA that you loaded into your MT4 platform and drag it onto the chart of the currency pair that you'd like it to be applied to.
The window below will pop up - In order to have trades executed on your behalf automatically be sure to select "Allow Live Trading" before clicking "OK"
Your EA is now attached to the currency pair on that chart, but is not yet enabled to place trades. In order to activate your EA you must click the "expert advisor" button located top center of the platform. The button should show a green icon when active and a red icon when inactive. See images below.
There will also be an icon in the top right hand corner of the chart to show EA status.
Now that you have loaded your EA onto the chart it should start executing trades as its code is programmed to do.