Rowenta FOCUS STEAM IRON DZ5164 DZ5164U1 user manuals
will give their specific instructions.
Rowenta has a kit, including a paste cleaner for iron soleplates, available from Amazon.
Home made cleaners include a paste of baking soda and vinegar. Rub on, let sit, and wipe with a wet cloth. (Some add a drop or two of dawn dishwashing liquid)
Another home made cleaner is the Mr. Clean Magic eraser, thoroughly wet, and rubbed over the soleplate.
Make sure to wipe the soleplate with a clean wet cloth at the end to remove cleaning residue.
Clean your iron's soleplate while the iron is cold, and don't use something scratchy like a steel wool pad, to avoid scratching the surface.