Navigate to the database you want to update and apply any filters/searches/queries you would like to use during the mass delete. Deleted records are unrecoverable so make sure you're only selecting records/contacts/content you absolutely want to delete.
Click on More to open up a drop-down menu. Select Mass Edit/Delete.
You'll see the Mass Edit features as normal on the left side of the webpage but will also see an extra option to delete selected records on the right. Press the red button to continue your mass delete.
Tip: Make sure the number of records at the top of the page seems roughly correct. You may need to readjust your search queries from the database page if anything seems off.
Clicking on the button will prompt the user with a CAPTCHA code. Once you complete this step your mass delete will start. Track your progress on-screen or come back later.