I have a folder on my file computer called CAD Custom files: In this folder I have all my customizations, ie. hatch patterns (*.PAT), drawing templates, PC3 / CTB files, and so on. My path is C:\HD Admin\CAD Custom Files. My advice is to create a folder like this so you can easily share files or recover after a system failure, ie. everything is in one spot.
To get AutoCAD to find these files, you need to add your equivalent of "C:\HD Admin\CAD Custom Files" to the list of directories Autocad uses to store its support files in:
In AutoCAD, enter OPTIONS on the command line;
The top left tab is "Files", and the first item on the list is 'Support files search path": Select "Support files search path" and click the "ADD" button (top right).
On the right side at the top is the "ADD" button. It will give you another line, and you can paste the relevant path into the spot created. AutoCAD probably needs to restart after this in order to find the hatch pattens, but they should show up at the end of the standard list of hatches.