Yes you need a Visa BEFORE YOU TRAVEL. either you get one or
Make an application for VISA ON ARRIVAL. The way of getting a letter visa on arrival is - The sponsor of yours must submit an application to the immigration at the airport with your name passport number , ex. date, purpose of your trip and the intended date of travel.
The immigration will say " please allow the passenger to board, visa will be issued on arrival " sign it and stamp . This letter must be faxed or emailed
to you and you should carry this copy of the letter.