What is this message means? " This file is too big. Files must be less than 1,500 kb in size.&

What is this message means? " This file is too big. Files must be less than 1,500 kb in size."

I used to download a themes from Elegant themes and i just followed the proper instructions and i just receive this message after i clicked the INSTALL NOW button and the message above appears.

Here's the screenshot and also the url: http://blog.prosper8dotcom.com/wp-admin/network/update.php?action=upload-theme

I just wanted to know how can i resolve this message issue. Please i need a helping hand.

Thanks a lot and more power.