how can I easily find and delete photos in my photos library?

It depends on which photos you wish to delete and why.

There are a number of methods of 'finding' photos:

• if you know the filename you can use the search bar
• if there are a particular group of photos you want to find then the best way is to create a smart album, you'll find it under the File menu. You can then set rules for finding photos, e.g. photos taken between a particular date, by location, size, file type, etc
• you can scroll through your photos and delete the photos you do not want individually
• if you are trying to delete duplicates then that is a bit harder and there are numerous threads on this forum setting out the various ways of doing this

Once you have found the photos you wish to delete you can select either a single photo or a group of photos and press delete or CMD-backspace. This will move them to the Recently Deleted folder and after 30 days they are removed from your album permanently.