How to delete discontinued items

Hi everyone! This is my first post so please bear with me.
I'm a online business owner and am trying to figure out how to delete
whole CSV files which contain discontinued items.
I was told by yahoo store customer service to take my store inventory and uploaded it to excel (lets call that excel A). Now, I received a email containing a CSV file from my wholesaler with discontinued items which I saved to excel ( lets call that excel B). I would like to know if there is a way to take "excel B" and import it to "excel A" so that I can delete all 148 items at once.
I've been deleting them one by one and that takes way too long. Especially since I am constantly receiving emails of discontinued items, I just can't keep up. Thanks to everyone for taking the time to read this.