Buy or sew a bag made of burlap or cheesecloth. An old pillowcase works really well for this.
Place one or two shovels full of compost into your bag or pillowcase and tie the top closed.
Place your bag into a large lidded plastic garbage can.
Fill the garbage can with water. Place the lid on and let stand for 3 to 4 days.
Remove the bag from the garbage can. The liquid left is your liquid fertilizer. If the water is a very dark color add some fresh water so the color is a light to medium brownish color.
Use a watering can and put around the base of your plants every 2 to 3 weeks. If the soil is very dry water the liquid fertilizer down to a 50-50 mix with plain water or water your plants first to wet the soil then apply the liquid fertilizer. If you use this with very dry soil you can damage your plants.