where and how should apply for the Visa?

Is it possible one person refer to apply Visa for dispathing team(5 persons)?should we pay any money?how many days will take time for Visa issueing?
We are a steel Co. in Iran and have bought Know How from china.now we have invitatin re dispatching our experts for visit from a similar Co. in Cina.Thanks and Regards,
F.Khoramroudi / Commerce Manager