Answer for USA, Canada and countries running a 60 Hz supply service.
Back at the Electrical Panel. There should be a 220 breaker for that line to power what ever. Remove the 220 breaker switch (make sure the main power switch at the top of the box is off) and replace with two 120 breakers which are actually called 15 amp and 30amp
When you use the term "step it down" that is electrical terminology when talking about transformers. If that is what you mean any 2:1 ratio transformer can be used as long as it is sized for the load on the secondary side of the transformer. 120 volts x amperage needed = Watts (VA).
If you are talking about electrical panel distribution breaker change from 240 to 120 then read the following.
Do this electrical work only if you feel confident that you can do it safely. If not then this is the procedure that an electrician would use and you would be able to follow what he is doing.
Again an electrician should be your first choice. If you consider doing this the first thing is SHUT THE MAIN BREAKER OFF. Use an auxiliary light source to see when working in a dead panel. Always keep in mind an ARC FLASH ACROSS HOT MAINS HAS ENOUGH HEAT TO PEAL THE SKIN OFF OF YOU.
Before an explanation of how to do this you should keep in mind that this is for a single receptacle only. If any other receptacles are on the same circuit they will also be changed to 120 volts.
The existing two pole breaker in the distribution panel that is to be replaced should not have a larger rating than a 15 or 20 amps. The wire size from that breaker will be #14 or #12 respectively. The final results of this project will leave you with a 15 amp 120 volt receptacle and one spare 15 amp breaker in the distribution panel.
That said OK, any 240 volt outlet can be changed to 120 volt by removing the white wire from the 2 pole breaker and inserting it into the neutral bus bar. Remove the other wire (probably black) from the breaker.
Remove the 2 pole breaker from the breaker panel.
Install two single pole 15 amp breakers into the hole left by the 2 pole breaker. Leave both of these breakers turned off.
Connect the black wire that came off of the 2 pole breaker on to one of the new single pole 15 amp breaker.
Re install the cover to the electrical panel, this end is finished.
At the old 240 volt receptacle, remove the existing device and install a new 120 volt receptacle.
Materials can be purchased at local building supply store. Remember to take the electrical panel data with you so you have the information for the 2 new breakers.
Once you have the new 120 volt receptacle installed, identify on the electrical panel door what the breaker is used for.
Leave the unused breaker in the off position.
Turn the new 15 amp breaker on.
Turn the main breaker back on.
Test the new receptacle with a lamp to make sure every thing is OK.
As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.
Before you do any work yourself,
on electrical circuits, equipment or appliances
always use a test meter to ensure the circuit is, in fact, de-energized.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.