Block heater location

Oil pan may be aluminum most block heaters are put in place of freeze plugs. A magnetic one should go on block by water jacket which would be on side of cylinder.

On the 1.6. If it has a factory block heater it should be in the freeze plug location above the oil filter. Magnetic heater would stick to the block if you can find a place that is flat enough.
If you wanted one that was not real hard to install you could opt for a heater hose mounted tank style or a lower radiator hose unit.
With them you can use a couple hose pinching clamps to block the water, cut the hose, install the heater unit, remove the clamps, route the power cord, and you are done.