Just in case you're NOT being sarcastic...

One of the biggest parts of painting is the prep work. And part of the prep work is making sure that your paint will actually stick to the surface. Glossy surfaces suck for painting because the gloss layer of anything is essentially a protective topcoat. Easier to clean, looks beautiful when done right, mold and mildew resistent (for glossy paints), but shitty to paint over.

There's a few ways to degloss:

TSP: mix 8oz liquid TSP (can't recall the ratio for powder TSP) with 2 gallons of hot water. Put on gloves, glasses, mask, etc. Wipe on walls with sponge. Wait for it to dry. Wipe down surface if necessary with warm water, usually needed if you use powder TSP.

Sandpaper: LIGHTLY sand the surface, just enough to make it rough. Use something like 400 grit with light pressure. Remember: the glossy coat is just the top layer.

Primer: Some primers, like Zinser 1-2-3, can stick to glossy surfaces. A coat or two of primer and you're ready to paint.

Please note: sometimes on exterior paint, glossy paints on metal or concrete have a good chance of being oil-based. You still need to degloss, but if you're painting with a water-based paint, you NEED to prime. Otherwise, it will chip and peel.

Not sure if it's water/oil based? Look at clean up instructions.

Soap and water = water based

Mineral spirits/acetone = oil based.