We currently support Stripe, with more options like Paypal and DIBS coming soon. Contact us if you would like us to add to that list.
Stripe requires a bunch of info from you to set up your account. Be prepared to have your bank account info, organization number and various other info for yourself handy. But, assuming your have all the info you need, it's easy peasy:
Go to your Builton Dashboard.
Go to Settings, choose Payment Provider and select Stripe.
Fill in all the bits.