Go to 'Payment options' and set it up there. Offer Bidpay as one of your primary choices and copy the code.
To go even further, you can remove Paypal as the 'default option' and force someone to choose. Or remove Paypal & leave Bidpay as your option, to a whole selection of your items. It will work and you'll have good sales where the money deposits direct to your bank withy Bidpay.