Hi I have to ask that my fiancé just received k 1 visa and the passport.. I have to ask what would be the next step.. is that he has to come here before six months and get married in 90 days or is that the first six months are for visa and 90 days are considered separately?

They are separate. A U.S. "visa" is solely for entering the U.S. He can use the visa to enter the U.S. any time up to the day it expires. When he enters, he will be given a duration of stay of 90 days. The visa is irrelevant after one enters the U.S.; it's the status given by the border officer that matters. The K-1 is a single-entry visa, so it is cancelled after entering anyway.

K-1 visa is a single entry visa, valid for 6 months from the date issued. That means he has to enter US within 6 months.

After entering US, you two must be married within 90 days from the date he entered US.