You’ve got a lot of work to do before you can paint your kitchen cabinets. Be sure you are up for this! Information can be found here.
The first thing to do is to cover your countertops with paper or a tarp. Use masking tape to tape the paper to the wall. See here for information about Using a Brush to Paint Kitchen Cabinets.
The one thing that will ruin your cabinet painting job is if you paint over dirt. Paint will not stick to dirt and oils.
The cabinets in a kitchen quite naturally have a lot of grease build-up on them from years of cooking. So all the surfaces will need to be thoroughly cleaned with a grease-cutting detergent. Once they are free of oils, then wipe them down again with clean water, then wipe them down again with a dry towel.
Once cabinets are absolutely clean, it’s time to sand them gently. Luckily, you don’t have to get down to bare wood; you just have to get the slick finish off. This is what allows the new paint to stick—tired yet?
Better than doing all these steps is this: call a local professional cabinet painting company. They will do all of this, and you are rewarded with cabinets that look like new.