The placeholder for the magnet is built with the slicer in Bambu Studio (negative part). You can change the size if you like or remove it (to print without a magnet). There's an auto pause at 20 min 59 sec (layer 12). This pause is meant to put the magnet into the placeholder.

magnet size: 29,5 mm x 29,5 mm x 1,7 mm

placeholder size: 29,6 mm x 29,6 mm x 1,8 mm

The magnet fits nice and tight. There's no need to fix it with superglue. I can't find the exact magnets I bought, but these magnets seem to have the same size as mine.

I recommend glueing the top side of the magnet for a better grip for the upcoming filament layer.

While the print is auto paused, put the magnet into the placeholder (hole) with the glued side on top. 

In my case the magnet slides into the shape perfectly.

Then continue the print.