It's pretty simple in PSP...
I have PSP9 so I think it's real close...
Open the layers in PSP and turn off each layer until you get to the color you want to use.
Then select the Foreground or Background Pattern in the Materials box.
When you click on the color itself, a popup window opens that lets you choose color, gradient or pattern. Select Pattern.
Now you will see a dropdown box with a bunch of patterns and the color you have open in the screen will also be there in the box to select it.
Thats it.
If you want each color as a pattern to be there all the time without opening them all the time, you need to open the Megapack.psp and select each layer one at a time in the layer pallet, click and hold down while you drag it out into an open area of your screen, then a little plus sign will show up and you can let go. Now hit File and Save As and name it anything.. but save it in your C/Program Files/Jasc Software Inc/Patterns folder and do the same for each color... now when you click the pattern tab in the Materials editor, that color pattern will always be there in the dropdown box.
If you have any questions, let me know... I will be glad to help if I can.