How do I install same app twice??

I want to install some app twice because i need to handle two account at the same time not doing log in and log out.
I hard that I have to change the package name of the app but i dont know how.

can i some how do it with titanium back up? if not, its ok

ill be very appreciate if you could teach me how to do it.

if im making this thread in wrong place, would you mind telling me where to make this kind of thread to??

thanks XD