Powering up is a long-term investment.
1)Imagine you have 10 steem coins, it would fetch you 20$ if you sell( lets assume 1 steem costs 2$). Now if you power up, the coins the coins are with you and you get more income or coins as curation reward. It's just like not eating the apple and making a tree out of its seeds.

1. Direct selling of steem coins would fetch would instant profits but it is a short time one.

Now to power up.

1. Login to your account.
   2)Go to your wallet and convert your earning (SBD to STEEM) by clicking market in steem dollars.
2. Covert then to STEEM and click power.
   The process is done.