You can also download the flixbus app and purchase
If you are in Las Vegas you will have to make your purchases online or over the phone. Compare Megabus schedule and prices before committing if you care about the best chance for a better quality experience. The Flixbus lack of infrastructure extends into management and customer service areas and I've heard more than a couple of their drivers complaining about working conditions.
Go on line or 7-11's sometimes have them
Download the app and then you can buy tickets
You pay them over the phone. Call them first to get the times and prices
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