You can withdraw it from PayPal and then use it. Why are you using Western Union, though? Online sales that require Western Union payment are very likely to be fraud.
NEVER use Western Union for online purchases. Only a scammer will ask for it Every single Western Union office has a poster warning customers to NEVER use Western Union for online purchases and to ONLY use Western Union to send money to trusted friends and family members A legitimate retailer will always accept Paypal and/or credit cards so you are protected if you don't receive what you ordered. Anyone asking for Western Union has no intention of sending you anything and will just keep your money. They ask for Western Union because it offers NO protection and can never be refunded. These scammers set up fake websites, ask for Western Union, steal as much money as possible over a 4-6 week period, then close the site and disappear with everyones' money. Then they open a new site under a new name and continue the scam
Paying by Western Union online.......Don't do it!!!!!!