You can link a PayPal account to your StubHub account directly from your profile or at checkout.
• Linking a PayPal account 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
• Linking a PayPal account at checkout
1. At Review & Buy, click Add a new payment
2. Choose PayPal
3. Follow the steps