You need to sing in on Radario website to have the possibility to buy any e-ticket for event shown in the list. You can sign in via entering your email, as well as via your Facebook or VK.com profile plugin. You need to press the Enter button in the upper right corner of the window.
At any rate, while you buy tickets, you should enter your email, because all of the tickets you buy are sent at your email address. Before the show you should either print your ticket (if the organizer’s security policy requires that) or show it on the screen of your smartphone or tablet PC while entering the concert.