You have two options:
Install Tampermonkey for Chrome;
Click the script to install it.
2. Vanilla Chrome
Copy the code and save it to a file called anything.user.js;
In Chrome, go to chrome://extensions/ (Tools > More Tools > Extensions);
Open the folder you saved the script to and drag it onto the Extensions dialog.
Bug: You didn't escape the title's HTML.
I've been using this plugin for a long time, just noticed it today. The title was "How to add general keyword to <select> ..." I think it will break too on other tags.
I think you should make a fix.
As you can see, I think the <ul> <li> situation in the plugin have too much of a ...