Developer Key can be seen in right side of http://www.oxwall.org/store/dev-tools page.
For Plugin key, you can randomly check in key availability.
Then only the event plugin can be installed into your site second time with new features.
In Oxwall Plugin Development, Each plugin must have unique plugin key.
Open Events Plugin, Go to plugin.xml and change the following values.
<key>event</key>
and
<developerKey>e547ebcf734341ec11911209d93a1054</developerKey>
I believe this is sufficient to answer your question