This is a two part process. It's not hard, but it may be confusing the first time you do it. That's why I'm sharing a simple step by step process of how to transfer your Steem or Steem Dollars (SBD) to Steem Power.
Step 1. Goto your Steemit Wallet
Step 2. Click on the big blue button that says 'Buy Steem or Steem Power'
Step 3. Choose which one you'll be transferring, Steem or Steem Dollars, in the dropdown menu on the left.
Then choose to receive Steem Dollars in the drop down menu on the right.
... and type in your Steemit username under that area.
Step 4. You will be provided with a memo code from @blocktrades .. highlight and copy the memo code.
Step 5. Go back to your Steemit wallet.
Step 6. To the far right of your Steem or your Steem Dollars, click the little grey arrow and choose 'Transfer'
Step 7: Type in the amount of Steem or Steem Dollars you're tranferring into Steem Power. Type in where you're sending it, which is to 'blocktrades'.. just type it like this: blocktrades ... and in the memo section, paste the memo code that you copied a moment ago.
Step 8: Go back to your Steemit wallet, within a minute of making that transfer, you will see the new amount of Steem Power deposited to your Steemit Wallet from @blocktrades.
If you have any questions about this process, please comment about it and I will answer your questions.