commerce_node_checkout

I've installed commerce_node_checkout but I don't manage to get it to work. I've tried to find some detailed description on how to use it, i.e. how to setup the content type, user role access etc. but without any success.

Is there anyone out there that can pitch in and give me a quick quide on how to use the module?
rgds
Jon

Installed commerce_node_checkout on my site with unexpected effects. Now I cant access, create or edit contet types. I get the following error that points to the comments module

Additional uncaught exception thrown while handling exception.

With this as the original description

PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT COUNT(cid) FROM {comment} WHERE status = :status; Array ( [:status] => 0 ) in comment_count_unpublished() (line 314 of /var/www/vhosts/mysite.com/drupal/modules/comment/comment.module).