OK. this is the first time i hear about Magic Lantern.
I don't really understand what Magic Lantern does. ..I had read about this on their site but i still not understand.... I have some questions:
- how do i install this soft?? like a regular camera firmware 
- is a firmware extension??
- what is does to stills??? ( i am not interested in video)
- after installation in camera menu appears new features, selectable features??
- it can be uninstalled?
A clear answer will be very appreciating . PS. English is not my native language.
Thanks,
It would be better if you'd check this forum for an answer or look into documentation but here you are:
- how do i install this soft?? like a regular camera firmware

- you put on a CF card, while booting a camera it looks for a autoxec.bin file on a cf card and loads it into the memory. The original firmware works as well at the same time
- is a firmware extension?? - no, it's independent open source software working with firmware
- what is does to stills??? ( i am not interested in video) - better check dicumentation, it's a lot of stuff
- after installation in camera menu appears new features, selectable features?? - yes. there is another menu with submenus and twice or three times as much options as in original firmware
- it can be uninstalled? - you remove from the card, you remove at all. You can boot a camera without loading ML at all