You can choose Venmo as you payment method while using your mobile device. Tap the PayPal icon at checkout, log into your PayPal account, and simply select "Pay with Venmo" from the options.
Please keep in mind that in order to see the option to pay with Venmo, you will need to have Venmo currently installed on your phone and not have PayPal OneTouch configured. For more information about how to change PayPal OneTouch settings, please see this support article.
Have more questions about how Venmo works? Read more here.