Unfortunately Cinnamon does not appear to have this functionality, (yet?). It only shows a panel on your primary monitor. There are several issues on the project's Github page that are requesting it.
Please add your support there, for example this issue:
Taskbar on second monitor #130.
There has been some interesting developments on that thread.
I wrote a custom extension, I took inspiration from the 2panelsbottom
extension on linuxmint.com, I also created 2 custom applets that are
essentially copies of the window list applet that comes with cinnamon,
only these show only the windows on each monitor, you also need 2
because as far as I know you cannot have 2 of the same applet loaded
at any given time.
I will write out some instructions and upload the extension/applets
somewhere later tonight.
Which was then followed up by this:
This could be great. Currently using two monitors, have to move the
mouse all the way back to the other screen to access the list of
windows. Is there a better way?
Along with this suggestion:
have a look at morePanels-Extension
http://cinnamon-spices.linuxmint.com/extensions/view/30 You can
configure top and bottom panel for each monitor separately. with the
window-list-multi-monitor applet you can get up to 2 panels per
monitor and different window-lists.
Attention: the extension makes heavy use of monkeypatching. Because i
have to overwrite a lot of functions. The two panels are hardcoded(!)
in the layoutManager, appletManager, the main.js file and so on.
using it at Cinnamon 2.2
Just so it's clear. The 2 extensions referenced are as follows:
Dual Monitor Panels
Window List For Multi Monitor
This extension modifies the "Classic" panels layout on dual monitor
systems so that the second panel appears on the secondary monitor.
Use in conjunction with the window-list-multi-monitor applet I also
created and you'll have more of the traditional gnome 2 multi monitor
experience much of us used to have.
This applet should be used in conjuction with dual-monitor-panels
extension I wrote to create more of a gnome 2 experience many of us
dual monitor users once enjoyed.
The extension is simply a fork of the stock Window List applet, but
you can add 2 instances, and configure them to show only the windows
from one monitor.