I want to change my wardrobe from being varnished to paint.
Sand the wardrobe lightly, paint with a stain-blocking primer, use a tack cloth to remove all sanding dust, then paint in the color of your choice. You might even be able to forget the sanding portion, but I find it's always best to do so.
Hi there, here's a lovely tutorial that explains in quite a bit of detail how to go about it - https://www.wikihow.com/Paint-over-Varnish
If it's in good shape, scuff the current finish with fine steel wool. Clean with TSP. Prime with either Kilz or Zinsser. Then paint.
Lightly sand with 220 grit sandpaper to remove any shine. Prime with Kilz primer. Then paint your color.
Here's a post that might help - https://homeguides.sfgate.com/paint-over-previously-stained-varnished-trim-40250.html
The biggest tip that I can tell you, is to use primer that is shellac based because it's made to adhere to a varnish type surface. This will ensure that your paint will stick successfully as well.
Here are some tips: