How to change web.config file of a different web site?

[Laraliflerm]

I have 2 web applications:[*]Main Application[*]Self PortalI want to change the web.config file of the Self Portal from my Main Application.In the main application I get the Self Portal URL \[code\](for example: http://servername/SelfPortal).\[/code\]How can I open its configuration file and edit it?Thanks,Inbal.