use the lasso tool (freehand) to select the parts that you want to add noise too

I selected both eyes and mouth and nose

TIP: TO SELECT MORE THAN ONE AREA HOLD YOUR SHIFT BUTTON DOWN WHILE DRAWING

go up to selections--modify- --- expand by 2

now click on shift +d and make another copy of your image

on one copy do this:

now go to effects add noise and add noise with uniform of 20%

now go back up to selections and select none:

go to layers and merge all flatten

now copy and paste your 1st image to animation shop

go back to PSP and go to the image that Does not have noise on it

copy and paste it as shown below in animation shop

now click on view animations and watch what you new image does:

you should have something like this:

enjoy

Nip