They're all optional.
Comma-separated two-character state abbreviations to restrict the search to - i.e. "ME,NH,VT".
An address as your search around. If this is included, results will have a "distance" property that represents how far away each result is from the given address.
Restricts search results to those within distance miles of loc.
An exact USAC permit # to match, i.e. "2014-2735".
The page of results to start with, counting by 100. i.e. a startpage of "2" will return the 200-300th results for that search, if they exist.
Restricts search to results within a given calendar year (i.e. "2014"). If absent, results will include all future events.
All you need to do is enter a BikeReg event ID (eg, 19208). You can't use a "fancy event ID", like "2015limerock". You can get event IDs from the all events API, under the "EventID" column (go figure).