Answer compiled from the comments on the question.
In China there are different rules in different parts of the country, so you will need local knowledge to get the answer.
Best ask your host, if they have had earlier visitors who needed to register they will know which station to use. In need, visit the nearest police station and expect to be send on to an other station, which may be farther away but in the right district or suburb.
Also prepare to be send back to the place you stay for an other bit of information or even a signature or stamp of your host.
Also expect long waiting times and repeated visits to the same or a near police station, as your time will not be valued as much as their 'traditions'.