It won't take long and the result is amazing, I can guarantee it!
Step 1: 5mm Magnets
For this instructable, you'll need 5mm diameters magnets. I found mine on the web, just look for something like "5x3mm N50 Rare Earth Strong Neodymium Magnet China Magneto Store" for example. Ali is my favorite magnet provider till now but I'm sure there are a lot of other sellers.
Step 2: Choose Your Bricks
Step 3: Almost Done
Step 4: Pressssss
Align the magnet with the central hole and press till it fits!
Step 5: Done
If you chose the right diameter, the magnet will stay in place. You now have the greatest magnet ever :-) Repeat as much as possible and place them everywhere!