Pay a wallet address in bitcoin
One way is to buy the bitcoin with fiat (cash) through localbitcoins.com (find a seller with at least a few transactions and 100% reputation). Have the bitcoin fraction you are buying delivered by the seller to the address you want. Just be very sure to get the address correct. You can verify that the funds reached the address by checking on any bitcoin block explorer, such as blockchain.info.  Once you verify the bitcoins are the address you want, you can pay the seller.