Procedure for tickets

Dear Team, can you kindly show me the exact steps to purchase the tickets, collect them and entry in the Forbidden City?
I mean, considering that I am foreign visitor:
How can buy the tickets?
Can I pay by Paypal/Credit Card?
How I can collect the tickets?
How can entry in the Forbidden City? (I mean, go with the tickets, only with Passport, go to some reservation to the ticket office and then take tickets.....)
Sorry for many questions but I don't want to take risks!
Have a good day,
Matteo