You're not quite using the "jargon" I'm used to, but I think I know what you are asking. I think you have recently bought and connected an external hard drive unit to use for data storage. However, you can't find it in Windows, not even in Disk Management. By the way, Disk Management is a small application, not a file or folder.
Usually the reason here is that the HDD needs to be Initialized. That involves two steps, but very often they are combined into one process. The two steps are to Create a Partition (that is, define a region of the HDD - could be all of it, or just a smaller part - to be used as one "Disk" in Windows with its own letter name like F: ), and then to Format that Partition (write the File System files so that it is ready to use all its space). These processes can be done easily in Disk Management, but you may need help on where to look.
For starters, read WyomingKnott's Sticky at the top of the Storage ... General Discussion Forum, here:
The key is to look at the two large panes on the right of Disk Management. First, both SCROLL so you can see all they contain. The Upper Right one shows you all the storage devices Windows understands already and is using. The important one for you, though, is the LOWER RIGHT pane, which includes devices Windows can't use yet, like a brand new HDD. Find your new external unit there and RIGHT-click on it to get a mini-menu that allows you to Initialize your unit. When it is done, back out of Disk Management and reboot so Windows updates the Registry, and your new unit should be ready to use in My Computer.