1. You can use the Help menu in PSP to learn a lot about scripts and scripting - although it's a tad obtuse until you understand the new vocabulary;-) Be connected to the internet and click Help>Help Topics. In the browser window that opens, in the upper left corner, click on "Search". Type Scripts and click "Go". If you can't see the full line of each topic listed, click and drag the bar separating the list of topics from the main pane to the right.
Basically, you're going to put your scripts in Start>Documents>My PSP. PSP should be closed when you add anything to the My PSP folder. (It won't hurt anything if it's open. It's just that for the new things you add to appear in the program, the program has to scan for them and it only does this when you launch it.)
The "My PSP" folder always stays pinned to the beginning of your group of folders so it's easy to find. Inside this folder are all the other folders which make adding things to PSP soooo easy. Scroll down and you'll see 2 folders for scripts: Scripts - Restricted and Scripts - Trusted. The easiest explanation is that if you've gotten a script from a known site put it in the Scripts - Trusted folder. If you're not sure about the safety of the script, stick it in the Scripts - Restricted. Scripts not only do wonderfully magical things to pictures but, because they're written code, they can also contain malicious pieces of code. Restricted scripts, like restricted teenagers, are watched more closely;-) I've downloaded and use a couple of dozen scripts and none of them have ever blown up my computer;-)
Once you get your new scripts into one of the scripts folders, launch PSP and open a picture you want to use a script on. Now, click File>Script>Run.... The Script - Trusted folder should open. If you want a script in the other script folder use the dropdown at the top ("Look In") box of the dialog to open it.
A lot of scripts are interactive and, as the the script runs, dialogs will pop up every so often that will let you adjust something. At the beginning, when you're still new to using scripts, you can just click OK on them all. But, if you're new to PSP, it really helps to "play" with these pop ups just to see what changes they make.
Have fun!