You can't import BIP38 into Dash Core wallet directly, you need to decode it first.
Go to https://paper.dash.org/
(optional, good for security) Save locally, disconnect from internet
Go to "Wallet Details" tab, fill "Enter Private Key" and click "View Details".
"Enter BIP38 password" field should appear so fill it and click "Decrypt BIP38".
Grab "Private Key WIF" and import it as usual - open Dash Core -> Tools -> Console -> "importprivkey <yourprivkeyhere>"