How to sign a message with my passphrase?

Solution: The lisk-cryptography package in Lisk Elements offers an easy to use function for signing any message.

const stringToPrint = cryptography.signAndPrintMessage('Hello Lisk!',  'robust swift grocery peasant forget share enable convince deputy road keep cheap');

The first argument is the text you want to sign, the second argument accepts your passphrase.
The reference can be found here