Hey! If you have STEEM in another Wallet, on an exchange, or on another Steemit account you can send it to your current account. On Steemit you just go onto the Wallet page, click on your STEEM balance, then on the drop down click TRANSFER.

Then type in the Steemit username you want to send to and the amount. When transferring from Steemit to an exchange, you will always have to fill in the Memo. But sending to a Steemit account only requires the Steemit username.

I'm still not sure the best for converting SBD to Steem. I know you can do it via the "Convert to Steem" button or at the Market. https://steemit.com/market So far I just use the Market to instantly turn SBD to Steem. I'll be looking into which is better money wise.