I need to free up space by deleting photos in iphoto

Select the photos in Photos (where you posted - if this is truly about iPhoto then post back as it is a bit different) and press the delete key (or right click on the selection and use the delete "n" photos command) then under the file menu ==> recently deleted click delete now

And if you still have the iPhoto library you need to delete the same photos from iPhoto as the hard links keep the image on disk until all links are removed - or if you are positive you do not want it delete the iPhoto library (however I suggest you wait a while just in case you want of need it)

and you do still have iPhoto - it is in your applications folder - if you're not up to date (version 9.6.1) see Get iPhoto 9.6.1 if you didn't update before OS X 10.10.3

And never, ever do into the Photos library directly and delete anything using the finder - doing so will corrupt your library and cause data loss forcing you to go back to a backup or start over with a new library

LN

Yes

If you want to delete all photos simply drag the iPhoto library to the trash and empty the trash - you can not undo this so be positive it is what you want

To selectively delete select the photos in events view and press the delete key - do not reorganize events before you empty the iPhoto trash and empty it every few hundred photos - sometimes having too large a =n iPhoto trash can cause problems - empty the iPhoto trash under the iPhoto menu ==> empty trash - then empty the system trash

LN

Not sure what is scary

You need to explain clearly since we can not see you

LN