how do i create a new folder in finder

Then there are 2 ways you can do it...

Drag that newly created folder on top of the HD icon which will move it to the root of the drive.

In Finder>Preferences>Sidebar, check the "Computer" box, back in finder click on Computer on left, select HDD in window, then create the folder.

The information below is in the Finder's Help menu. Your problem creating a new folder may be due to your not having the correct window activated.

*Creating a folder*
You can create folders to organize your files and applications.

In a Finder window, open the location where you want to create the new folder.
Choose File > New Folder.
To give the folder a new name, select it, then click its current name. Type a name for the folder and press Return.
If the New Folder command is dimmed, you do not have permission to create a folder inside the folder you opened.

*Changing the icon of a file or folder*
You can use custom icons for any file or folder in the Finder. You can create your own icons or download icons from websites on the Internet. Once you have custom images, you can replace icons for items.

In the Finder, select a file whose icon you want to use.
Choose File > Get Info.
Click the icon in the Info window and choose Edit > Copy.
Select the file whose icon you want to replace and choose File > Get Info.
Select the icon in the Info window and choose Edit > Paste.