How do you magnetise steel?
With a magnetic field
There are 2 common ways of magnetising steel.
First of all you can put it near another magnet and its magnetic field will interact with the steel, giving it a magnetic field of its own.
You can also make it an electric magnet by putting electric wires around it (the more laps of wire around the steel, the better magnet). If tou then turn on the power you will have a magnet.
Keep in mind that some steels doesn't have these magnetic properties.