How to buy Nohi bus tickets on line

I would like to buy on line Nohi bus tickets from Takayama to Nakaokogen-guchi (on the Route bus from Takayama to Shinhotaka Ropeway). I cannot find this kind of information on the Nohi bus website.
Anybody knows how to do?
If it is not possible to buy tickets on line, how can I buy tickets? Just going at the counter on the same day of departure?
Is there plenty of places in june? How long does it take to get off the train (from Tokyo), buy the tickets and take the bus? Would it be possible to catch the 11.40 bus, after arriving at Takayama by train at 11.23?
Thanks a lot for all (possible) answers!!

Reservation is not possible as it is a route bus ie local bus where you pay to the driver and stand when there is no seat.

Thanks a lot for your very helpful answer! I don�ft know how big are Takayama train and bus stations. Do you think we have enough time between the arrival of the train at 11.23 and the departure of the bus at 11.40? Thanks again!

That should be enough. The Nohi bus station is just like a minute walk from JR Takayama Station east exit (Norikura-guchi). The bus stop is exactly in front of where you buy the ticket.

Thank you very very much for your answer! One last question: can we bring our lagguage on the bus? Is june a busy period? Thanks so much!