If you don’t know much about storage, then I do not understand why you plan to build your career on it.
However, start by looking for “white papers” on the web, and reading up on various storage vendors.
Storage is an odd (unusual) choice by itself. There is a lot to learn, but unless it is coupled with an understanding of the types of storage used and the reasons for them, it is not going to help you much.
Bare storage covers things like disks, disk arrays (RAID), tape (yes, tape is still widely used), optical of various types.
Beyond that are methods of accessing: SATA, IDE/ATA, SCSI (of various types), Network Attached Storage, etc.
Then you have to consider what is reading and writing to this storage: Straight Operating systems (Windows, Unix/Linux, Manufacturer-specific O/S’s), Databases which use the underlying operating system and file system, and databases which manage the bare disk on their own.
I’ve barely touched the surface of what I know – AND when it comes to storage, I know very little. But I hope that this gives you some idea of what all is involved and where you should start looking.
If you are referring how to become expert to that certain area, you have to take a course preferably on hardware servicing which focuses on storage devices. However, you can also take online courses and learn through self studies and reading online tutorials and guides.