goto embassy

:embassy
ask for visa application
fill the form with your details, your vacation details
submit
wait until they approve your visa

for vacation - just need a reference of a person that will sponsor you in the U.S.
If you're flying under a tour company, just state the company's name.
How long, around a week or so, US visa is kinda strict lately. If you're not a Muslim, you should have no problem getting visa faster.

Advisable to apply visa first before booking ticket to US because they might not approve your visa fast enough.
ah, most tour company will handle your visa imho.