I made as you describe but when I insert in the console my BTC address private key it says that it's not a valid private key (error -5).
I write importprivkey
You know not to type the < and > characters, right?
I just tried generating a couple of BTC addresses and private keys using bitaddress.org and was able to import them using the 'importprivkey' RPC:
$ clamd importprivkey Kzf95MZgZ2ZGU4FWni6BmUpAaicu1oJSqpedeyqG4FBSdVNYfCPw '' false
$ clamd importprivkey L5YCDqiPNvvmTxPvnr9jPcNXubLCSTuSdviXeyJiAM22L72xBFs1
$
The first one is quick since the 'false' means not to rescan the chain to find any transactions involving that key. The second one is slow, but is what you'll need to do to claim your CLAMs.