You stake by transferring your coins from the exchanges to the temporary wallet.  All you have to do is that.  I encrypt all my wallets with a password, so each time I load up the wallet I have to unlock it in order for it to stake.  If you don't encrypt, it will begin staking as soon as you have mature coins (4-8 hours).  The reason I say temporary is because these tokens and wallet are temporary while they set up the assets on the Next Horizon (NHZ) Network in the near future.  Once that is established, this staking wallet will go away as we transfer our tokens to the Asset Network.  If you haven't checked out NHZ, I recommend it.  It is our future and claiming a small stake in that alt won't cost you that much (there's quite a potential there).  

Benefits?  It strengthens the POS network, and it's a way of getting "FREE" coins without having to do much of anything.  That's good enough for me!