How to import private keys
Caution: Be careful while transferring private keys. Wrongful handling can cause the loss of your Litecoins. Always make a backup of your wallet.dat before importing and exporting private keys.
Open the RPC console
Click on Help, open the Debug Window and switch to the Console tab.
Decrypt BIP38 encrypted keys
If your private key is not BIP38 (password) encrypted you can skip this step. If your key is BIP38 encrypted (starts with 6P) you need to decrypt it first before importing the key to Litecoin-QT. Liteaddress is one of the websites that can be used for this. Click on Wallet Details, enter your key and click on View Details. Now you'll need to enter your BIP38 password. You'll find your decrypted private key below the Private Key WIF QR Code.
Your keys are not being transferred to the Web Server. To ensure this, you can disconnect your computer from the internet and still use the website as normal.
Unlock your walletIf your Litecoin-QT wallet is not encrypted (not recommended) you can skip this step. To unlock your wallet you need to type in the RPC console:
walletpassphrase MyWalletPass 60
Change MyWalletPass to your wallet passphrase and change 60 to the number of seconds that you want the wallet to be unlocked. After that time the wallet will be locked automatically. Make sure to unlock the wallet long enough to do the next and final step.
Import the private key
Type into the RPC console:
importprivkey MyPrivateKey Lable
Change MyPrivateKey to your private key (starts with 6v or 6u) and for Label you can enter a name/description/label for the key (optional). The importing takes a few minutes depending on your CPU power. The import is done when an empty line appears in your console. Now you should be able to see the corresponding address to the imported key in the Addresses section.