This question is very broad, and I would firstly recommend that you do some reading on the background of Khums and its rulings.
A very brief reply to your two questions:
1. What items is khums compulsory on: (1) savings at the end of your khums year, and (2) items that you own but are new and have not been used all the way until the arriving of your khums day.
2. How should it be distributed: To be given to the office of your Marja' Taqleed, or his shar'i representative (wakil).
There are much more details, and as this is a fiqhi issue, you will need to refer to the fatwas of your Marja' Taqleed. I would recommend you go through this link, and familairise yourself with the topic: