Update:
With Jon's help, we discovered that BugMonkey 2.0.0.0 - 2.0.1.10 won't work if you have
Protect FogBugz Actions > Protect actions against Cross-Site Request Forgery
... disabled.

Regardless of whether you're using BugMonkey 2.0 or not, this is an important security precaution, and we'd advise strong against keeping that setting disabled.
The settting is underAdmin > Site Configuration > Advanced > Protect FogBugz Actions
If this box is checked, or you are using FogBugz On-Demand, then ...
Steps that should make a BugMonkey 2.0 customization run for you:
Installing the Plugin
- Upload the plugin (the plugin should already be available to you if you're using FogBugz On-Demand)
- Optional: Go to the plugin configuration (
Admin > Plugins > Configure) to allow your users to create their own customizations, or import them from fogbugz.stackexchange.com
Creating a Customization
- Create a new customization (
My Settings > Customizations > New Customization...) Make sure to change the name and description to something useful.
- Optional: Click
"Apply", and then "Rules for this customization", and follow step 2 from the next section. (This can be a more convenient way to set the rules for your customization)
- Save the customization (
"Save")
Applying the Customization to Your Users
- Go to the rules for that customization (
Customizations You Own > Edit Rules...)
- Select the group of users you want the customization to work for, click
"Add", and set the level ("Default Off", "Default On", or "Required")
- Click
"Done"
- Optional: If you made the customization optional for yourself, go to
"Your Available Customizations" and enable the customization.
- Optional: Refresh the page, or browse to a page where the customization is supposed to do something. Hopefully you'll see your customization in action!
Potential Gotchas:
You won't see the customization in the following cases:
- It's Default Off for you, and you haven't enabled it
- It isn't applied to you (e.g. you're an
Administrator, but you've only applied it to Normal users)
You can check to see if a customization is supposed to be running for you by verifying that it is listed in the "Your Active Customizations" tab.