Other than MTS, any time I install a script (using tampermonkey), nothing changes, I don't even know how to start looking for how to use them...
If you're trying to use things like panda crazy and hitforker they have an url that you go to in order to use them. If you're trying to use scripts for specific hits then make sure they are turned on in Tampermonkey or whatever you use. If they're still not working try only having one turned on at a time to see if they are conflicting with each other. I'm guessing it's the first one I mentioned though since you say MTS is working okay for you.
The video is two years old, so note that deleting scripts is now done by clicking the trash icon to the right of scripts on your Tampermonkey Dashboard. But installing scripts is the same, as is creating them. You may copy/paste scripts into the creator page, save and done. I assume you're using Chrome? Can you mention a particular script you're having trouble running? It may be obsolete since many scripts broke when the new Turker site went up. It may also be that you have scripts conflicting, or turned off. There are many reasons why a script may not work. Some scripts require you to go to a specific page for them to work, like HIT scraper or PANDA Crazy. You'll need to bookmark the page so you can go to the link with one click next time. Make sure you're logged into your Mechanical Turk account as some scripts won't work if you're logged off. Off the top of my head, these are a few things that may help. To find out which link works with your script, go to the page you downloaded the script from, and read the instructions, the link is usually posted there.