To run a test payment, you will have to use an alternate Paypal/payment processor account separate from the account used to collect product sales. If you try to purchase using the same account that your product is set up under, you will receive an error.
You will also want to ensure that your account is setup with US Dollars as the default currency. You can find out how to set your account up by reading this knowledge base article:
https://jvzoo.zendesk.com/hc/en-us/articles/206456717-How-do-I-set-my-Paypal-account-to-accept-USD-