Pretty simple, but you have to be using Firefox. Go get the Greasemonkey addon (yes, I do mean install it), and then (after restarting Firefox, like it asks you to), click the link for the script you wanna install.
That's about it, really. Next time, you won't even have to install Greasemonkey again, either!
Yeah, every once in a while I may update one of the scripts. When that happens, I'll put a note in here with a timestamp so you can figure out what's new. Feel free to let me know if one of my scripts stops working. Chances are, I already know -- if it's a script I'm still using -- but better safe than sorry.