Depends on what kind of computer you have. For Windows, assuming Python is in C:\python27, Twee is in c:\twee-1.7.1, and your HTML file is mygame.html which you've copied to the Twee directory, run the following commands from the Command Prompt:
set PATH=c:\python27\;%PATH%
cd c:\twee-1.7.1\
python untwee mygame.html >
mygame.twThis should create a file called
mygame.tw in the Twee directory that you can then import into Twine.