How do I get a visa for my fiancŽ to come to unite state?

Really depends on what country they are based in as to the actual process.
Be warned if it's Ghana or other African countries, it is most likely a SCAM.
Do NOT send them any money for this endeavour.

You don't really, They apply to the US immigration, normally though the local embassy for a visa. They are not very costly.

Often you bring her in on another form of visa and then ask for a change of status after she is here.