So ...

Upon activation, go to Settings => Simple Comment Editing to access the plugin configuration page.

As you'll see, there is only one customizbale parameter, the default time limit:

In other words, the plugin works out of the box. If you don't want to modify the default 5-minutes time limit, then there is no settings you need to change ...

Needless to say, you can define any time limit ... However, don't forget that your goal is to allow users to fix grammatical errors or taking back something right away ... So I wouldn't recommend a time limit which is higher than 10 minutes.

OK. Now let's see the result ...