Lock posts 'Lock post' dropdown not visible


This plugin is exactly what I was looking for i.e. lock down a student blog post submission.

However, I've installed it and activated on one of my sites but don't see any 'lock posts' drop down on the post edit page as described and shown in the plugin.

Should it appear automatically or am I missing a step? I'm logged in as admin. Do I need to login as network admin?
I'm sure the blurb said you can lock posts down to just admin.

Finally, another feature request for this to make it super useful.
Would be essential for large classes to 'bulk lock' posts, say by category. For example, our students are posting their marked entries to a specific category. If there was an additional admin page in Tools that could bulk lock all posts in a specific category that would be amazing. Save us hours.

Anyway, thanks again for what I hope is a great plugin!