The first step is to go through what you have - then determine how to store it.
TRY ON EVERYTHING you haven’t worn recently including shoes! There is likely a reason you haven’t worn something. If you don’t love the way it makes you feel - get rid of it. You’ll free up space for items you DO love.
Get rid of what has outlived its use, is ripped or damaged, or doesn’t fit your lifestyle. Anything damaged should be thrown out, or used as rags, not donated.
Are there missing buttons? Are the pants too long and need to get hemmed? Always have a place to put items that need repair. It is also a good idea to keep a bag in your closet where you collect dry cleaning so when you plan to drop off, it’s already together. A simple reusable grocery bag works.