How can I get a Tibet permit with beloyrussian passport living and working in Vienna, Austria?

Hello, my name is Kseniya, beloyrussian, but live and work in Vienna. Would like to go next year to Tibet and see a little bit China.
How can I get a Tibet permit living in Vienna?
Can I only go to Tibet with 5 travellers with the same natinality, Belorussian?
Or I can with my beloyrussian passport apply a Tibet permit by TTB and join china tour group to go with them to see tibet?

Thank you,
Kseniya