If you would like to install or use your own custom indicator and Expert Advisor, you can do this by going to File > Open Data Folder and open MQL4 folder.

There are experts and indicators folders within it and you will need to copy the .mq4 or .ex4 files into their respective folder.

For Custom Indicators or Expert Advisers, you can acquire from MQL4 website for free or with some cost.

For any troubles regarding to the programs you use/run on MT4, you may contact the developer of the program directly.