You can link a PayPal account to your StubHub account directly from your profile or at checkout.

• From your profile
  1. Go to Settings > Payment
     
  2. Under Payment options for buying tickets, choose Add a new payment option
     
  3. Click PayPal. Log in with your PayPal credentials.
  4. Select your billing address
• At checkout
  1. At Review & Buy, click Add a new payment
     
  2. Choose PayPal 
  3. Follow the steps