First off, visas are not denied, they are refused. If your visa is refused, then you will need to apply for a visa every time you wish to travel to the UK in the future.
You will need to send off your passport but that will be after you have attended your biometrics appointment.
The basic application process is:
Apply online, pay for the visa and book your biometrics appointment
Attend your biometrics appointment (you will need to take your passport and appointment confirmation sheet). It should take about 10 minutes for your photo and fingerprints to be taken.
Mail your passport, printed application, biometrics sheet, and all your supporting documens to the consulate. They must get there within 14 calendar days of the biometrics appointment date.
It can take up to 30 working days to be processed, but you can purchase the priority service for $150 from the Worldbridge website to get it processed in 48 hours. You shouldn't book any travel until you have your visa.