The https://drupal.org/project/google_cse module appears to be a dead project - the Drupal 7 port hasn't had any activity in over 2 years. If you want to use a Google Custom Search Engine (CSE) on a Drupal 7 site, what do you do? Turns out it's relatively straight-forward to just generate the CSE over on Google's website, take the code and paste it into a Block, and that's it.