I was just speaking with support and they were very helpful in explaining that Importing constituents in bulk can only be done via the database view.
As someone who has used other systems i think it would be good to be able to import constituents and non constituents in bulk (to an event) via the web view on Raisers Edge to an event as marking those attending one by one to an event when you have 200 participants is a very tedious task.
This can be done with a CSV template and headings.
I use Omatic Cloud Software to import into RE. It uses Blackbaud's SKY API functionality. So far it works well except Blackbaud has put a limitation on how many times a single constituent can be a participant to an event. That's a problem for me because we have multi-day events where someone can have multiple roles and therefore multiple Participant Types.