Once you have downloaded an MT4 Indicator it needs to be placed in the correct directory.
Usually your brokers folder will be c:\Program Files/(name of broker)/experts/indicators/ and you can place either the .mq4 or .ex4 file types here.
All .mq4 file types will automatically be converted to the .ex4 type by Metatrader as you load up the program.
Once the file is in its correct location you will need to load up your Metatrader terminal (or restart it if you already have it open). To load up an indicators simply choose a currency pair, with that currency pairs trading window open, select the indicator in the far left pane (under Custom Indicators) and drag it into the trading window. It will firstly come up with a settings window. Make sure you have “Allow DLL Imports” ticked on just incase this particular indicator wants to call up any dll’s.
You can also have a look at other settings under the “Inputs” tab. Most of the time you will not need to adjust anything here though some indicators allow you to alter the colours if you are not happy with their default settings.