You have the option to connect your store to one of three cc processors: Stripe, Square, or Authorize.net.
Additionally, you can provide your shoppers with the option to pay using PayPal. This means you can take one of these three approaches to transactions within your store:
- Accept All Major Credit Cards Only (w/ Stripe, Square, or Authorize.net)
- Accept PayPal Only
- Accept All Major CC + PayPal
If you go with number 3, then your customers will be given the choice to pay for their purchases either with their credit card (all major cc are accepted) or by logging in to their PayPal account.
This third choice would look something like this on your store's cart:
You'll find the option to connect your account to any of these providers under Settings > Checkout in your Store dashboard.
If you want to run credit cards with Stripe, click the Enable option to create a new account with them (you can also log-in to an account with them if you already have one). Creating a new account is painless and should take no more than five to ten minutes before you'll be able to start taking orders.
If you prefer to use Square, click the appropriate Enable option. You’re then given the choice of:
- Logging in to Square to immediately connect to an existing account.
- Starting a new account, which can then be used both within and outside of our service. If you start a new account, it’ll only take around five to ten minutes to get things going.
Square is only available to our Business customers, but a major benefit of Square is that their service can be easily used to process both in-person and online transactions. Stripe only supports online transactions. 
If you want to provide PayPal payments in addition to Stripe, you'll also enable PayPal. This process is incredibly simple if you already have a PayPal account as all you need to do is enter the email address on your PayPal account and you're all done. 
If you don't have a PayPal account, but would like to use PayPal, then head over to paypal.com and sign-up for an account with them. Once the account is established you can then connect to that account from within your Store settings.