I am a US citizen living in Reno Nevada and recieved a job offer in china

hello, I am from reno NV and received a job offer from a company placed in Zhongshan "Macau" with head quarters in Hong Kong... they requested a 3 month trial period prior to permanent employment. I have looked thru the descriptions but could not find a full answer . what is required to do this 3 month trial for employment...? what permits and visas for entry and exit?