This is how it is done: https://en.bitcoin.it/wiki/Wallet_import_format
And you can do it online at this site: https://gobittest.appspot.com/PrivateKey
And you can do it online at this site: https://gobittest.appspot.com/PrivateKey
Great. Thanks a lot. Is there any JS based substitute for this, like bitcore.io/playground/#/address ? Because this seems to be sending private keys to the server, which is insecured from user's point of view.
Download bitaddress.org
I'd go with bitaddress.org as well. Just click 'wallet details' and punch in the private key. Here's what that will look like:
