It's quite simple. Send the BTC in your localbitcoins wallet to your blockchain wallet address.

You may have given the seller your blockchain wallet address, but the seller wouldn't have sent it there. Once the bitcoins are released from escrow, they're sent to your localbitcoins wallet automatically. So just send those over to your blockchain wallet. Easy.

Go to https://localbitcoins.com/accounts/wallet/ and enter your blockchain wallet address and the amount you want to send to your blockchain wallet. Hope that helps.