Closets and Storage

Looking to add wood flooring to storage place under the house. We have small door on the side of the house that leads to our storage space. Right now the storage is just dirt with a couple of shelves built. It’s two small rooms but the second room is barely able to get into. Want to build flooring and and make the entrance of the storage larger so we can walk right into it. Also would want to be able to find out a way where we could utilize all of the storage space under the house. To get to the storage, we walk down the side of our house and there is a small door attached to the house before you reach the gate for the backyard. Not looking for anything fancy. Something simple that would do the job. Thanks!