I don't think you can do it from Payoneer. You can set up an account on an exchange that trades STEEM. You will first need to have some key trading pair currency like Ethereum or Bitcoin. You need to trade the Bitcoin or Ethereum for STEEM. Then you transfer the STEEM into your STEEM account. Each exchange is different, so make sure to get the type of cyrptocurrency that trades with STEEM.
If that is too difficult, click your wallet and click the down arrow next to your STEEM amount. Select "Buy" and you will sent to Blocktrades. From there, you can buy STEEM with Bitcoin, Bitcoin Cash, Ethereum, Litecoin, Dash, Monero, Dogecoin, BitCNY, BitEUR, BitShares, BitUSD, OPEN.BTC, or OPEN.Dash