When you click into the 'send money' tab at the top of the page it will ask for the email address of the recipient, the amount and currency of what you are sending.
It will then have two options underneath stating whether you will be paying for goods/services or to family/friends/gift.
Just select goods/services and hit continue, easy as that!
Goods/Services ensures that you are eligible for buyer protection and also ensures that any fees are taken by the seller rather than yourself
Hope this helps 🙂
