How do I paint dark pine furniture a light color?

Liquid sandpaper ( home store )rub on with rag let dry and paint away

You should use a deglosser to remove any sheen and dust that is on the furniture. You could make it lighter.. I suggest picking up one of those Rustoleum kits which has almost everything in the box except your brushes and rags. The prep materials and instructions are also in the box. The kits run for less than $100 on sale. If you are just going to paint it then you still need the deglosser, primer and the color paint you are finishing with.

Use Kilz first and then paint the furniture. Kilz comes in latex and oil. Check with the paint dept. which is best for your furniture.

Lots of ideas here.

https://www.hometalk.com/search/posts?filter=paint%20wood%20furniture

You only need to sand it if it has dents or scratches. Otherwise just give it a good cleaning w/Dawn dish soap mixed in a bucket of hot water, to remove old grease & dirt. Then dry it completely before applying your 1st layer of paint. You will likely need a couple of coats to cover the dark wood color. Be sure to allow each coat to dry completely before adding the next. Have fun! :)

Pick your favorite chalky finish paint or mineral paint and go for it! I would probably NOT do white as it will takes many coats to go over the dark finish.

You can check out how I painted a chest of drawers that was very dark into a light blue below. :)

https://letspaintfurniture.com/how-to-chalk-paint-a-chest-of-drawers/

find sandpaper it first, paint with primer... then colour of your choice

You absolutely do not need to sand if you use a deglosser/liquid sandpaper and follow the directions. Take this from someone who has been painting furniture for over 40 years. I usually do do 2 coats of deglosser to make sure I get it in all the crevices. Use a liberal amount of deglosser. You can paint your piece white or any other pale color if you use primer first. I would use a high quality bonding primer and do 2-3 thin coats of primer. Thin coats give much better coverage and go on smoother than one thick coat. Don't be concerned if your first coat of primer doesn't cover all the dark wood. The second or third coat will cover completely. Once you have good primer coverage, you can paint any color you want. I usually do a quick light sanding after the last coat of primer before applying paint just to make sure any small ridges of primer are smoothed away. After painting, I use a white sanding/polishing pad. This gives a luster to your paint finish and will not sand away your paint.

I like to use Fusion Mineral paint. Here is a post where I used it on an old door that I turned into a dutch door. https://lifeonsummerhill.com/diy-exterior-dutch-door/