Event types are only used if you have turned on events as a log type and set up logging badges for attending a “library event.” If you have badges that do this—not activity badges, but logging badges that log by library event—then you may let your readers select the type of event attended. The options they see will appear in a dropdown, from which they may select the type of event attended.
Event types are housed under Challenges and are not related to Recommended Events, which are housed under Content. When you navigate to Challenges > Event Types, you will see something like this: