Given that you are not a programmer, it's great that you were able to install this plugin. But I'm afraid that it's not going to work with ckgedit. This plugin creates HTML markup but ckgedit and Dokuwiki don't know what to do with it. If you want to align text, use the divalign2 plugin, which has a very simple markup:
https://www.dokuwiki.org/plugin:divalign2. Enter the markup into the ckgedit Editor; the alignment will not show up in the editor but will be displayed in the browser. So for instance, with divalign2 markup, this is what you might see in the Dokuwiki editor:
;#;
This is aligned center.
;#;
But in the browser, the markup disappears and the text is centered:
This is aligned center.
In the ckgedit editor you would do the following:
divalNLine;#;centerdivalNLine;#;
That is, in front of each of the divalign2's markup elements, you preface it with
divalNLine.This makes sure that ckgedit preserves the newlines which are required by the plugin:
https://www.dokuwiki.org/plugin:ckgedit#divalign2_plugin