Hallo I am very new on wpmu. i have already installed

Hallo
I am very new on wpmu.
i have already installed wpmu,with this page.
i have some questions
after install i cleaned my cookies and i would like to try register my website as a new user.
i done it with different mail. i become a login details. but i do not know what is the blog adress for new user.
can users select their own bloggin adress like edublogs.
example: mydomain.com/usersblog
if its possible can system check the blog name. (for duble) if blog adress already taked user must become a message.

and which steps must i follow.
Do you have a any todo list for begginners.?

i have fresh installed
thanks and greatings from germany