Click on File > Open Data Folder

Open MQL4 or MQL5 > Indicators

Copy the indicator file to the Indicators folder. You can drag and drop the file or use CTRL+C and CTRL+V manually.

Close the folder and restart MT4 (close and reopen MT4). In the Navigator, expand Indicators and find the one you want to install. Double-click or drag-and-drop it onto a chart. Click OK.

The process is the same, except in step no. 2, you’d open MQL5 instead of MQL4.