Your boarding pass will be available when you check-in online or in-person. You can check-in within 24 hours and up to 1 hour before your flight with your reservation code.
Once you have finished checking in, you have the option to save your boarding pass in apple wallet, or you can email, print or download your boarding pass from web check-in. Be sure to have your boarding pass accessible when at the airport.
More info can be found here.