When you create a account at BitcoinFog you will get a deposit address, you should copy this address and then go to LocalBitcoins and click withdraw and paste your BitcoinFog deposit address into the space provided. Once you have 6 confirmations by the network then your Bitcoin will appear into your BitcoinFog account and you can start to tumble your coins into your Silk Road account. Here is a paragraph from BitcoinFog explaining how their process works,