I read this without finding the solution: http://docs.python.org/install/index.html
On advice from http://for-ref-only.blogspot.de/2012/08/installing-beautifulsoup-for-python-3.html, I used the Windows command prompt with:
C:\Python\Scripts\easy_install c:\Python\BeautifulSoup\beautifulsoup4-4.3.1
where BeautifulSoup\beautifulsoup4-4.3.1 is the downloaded and extracted beautifulsoup4-4.3.1.tar file. It works.