You will need to find a suitable picture of your target first.
Facebook:
Downloading pictures on Facebook is easy.
Find a picture. Click on options and then download.
Instagram:
To Download pictures from instagram, use this site:
Instagram Downloader 4 Pictures
As of now the picture software has some problems accessing private profiles.
Work-Around
If everything else fails, you can always press "print" on your keyboard to do a screenshot.
Then open Windows Paint and press ctrl + v .
You should see your screenshot now. Just safe the picture as .jpeg and you are done.