It's pretty simple actually... just clean them as good as possible from any of the gunk from inside of the pumpkin, dry them in a paper towel, put them in an envelope and label as to date and what they are. Problem is, if the variety of your pumpkin happens to be a hybrid, which is likely since most are today, you may or may not have seeds that will sprout and if they do they may not produce true to the type of their source if at all... But, good luck at any rate...