Where can I buy a ticket for the river-cruise in Guilin and how can I get to Zhujiang Wharf

I´m going to Guilin in April for 3 days. I want to do a river-cruise from Guilin to Yungshuo (return by bus). Where can I buy the ticket for the river-cruise and how can I get to Zhujiang Wharf? Where is this wharf - in the near of the downtown of Guilin or outside of the town?
I don´t know the China-language and the China-letters. I´m travelling without group. Are there any problems?
Thank you very much !!!