Be extremely careful when importing or transferring private keys. You could loose all your coins if this is done improperly. Private keys should be imported only from self-generated addresses.
Click on Help, open the Debug Window and switch to the Console tab.
If your Anoncoin wallet is not encrypted (which is highly unadvised, please encrypt it now!) you can skip this step.
To unlock your wallet you need to type the following in the RPC console:
walletpassphrase MyPassword 60
Change MyPassword 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.
Type into the RPC console:
importprivkey MyPrivateKey Label
Change MyPrivateKey to your private key (which starts with 64, 65 or 66) 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 the console. You should now be able to see the corresponding address to the imported key in the Addresses section of the client.
Exporting a private key follows the same steps as above for importing a private key. For step three, instead type
dumpprivkey MyAnoncoinPublicAddress
Please store your private key in a secure location: If anyone obtained it, they would be able to steal all of your coins.