To add an Expert Advisor or a custom indicator, open the MT4 or MT5 platform and go to File => Open Data Folder. Then navigate to MQL4/MQL5 => Experts (for Expert Advisors) or Indicators (for indicators), and move the indicator or EA file in .mq4/.ex4 or .mq5/.ex5 format into the appropriate folder.
After restarting the terminal, your custom Expert Advisor or indicator will appear in the Navigator window. You can drag and drop it onto any chart using your mouse.
A properties window will then appear. Click OK, and the Expert Advisor will start running on the chart. You’ll see its name and the icon 
in the upper right corner of the chart.
If the icon looks like this 
, it means automated trading is disabled for the EA. Enable it in the EA’s settings and also in the platform’s global settings to allow automated trading.