IMPORTANT
Backup your database and your current theme before you begin with theme update in case something goes wrong.
There are different ways to update a WordPress theme. We recommend theme updating by uploading a new theme. It’s the same process as installing your theme for the first time. If you attempt to upload a new version of a theme that is already on your server through the theme section in the admin area, it will fail, and you will get a message that theme folder already exists.
The simplest way to update the theme is to delete the old theme first, and then upload the new theme. Make sure you have a copy of your old theme on your computer in case something goes wrong with the new theme.
Theme Updating via WordPress Dashboard

Step 5
Then click Upload Theme button and choose file cuckoolove.zip. Make sure this is latest theme version.Other Update Options
If you’re not willing to delete the theme, then before uploading new theme you should rename current theme folder CuckooLove to something like that CuckooLove-Old and then upload the new theme.
Remember that updated theme folder must have the same name as it was before updating.
How to Update Customized Theme
How to update the theme that has been customized or what if you can’t remember what customizations you’ve made? Check this useful online resource: How to Update Customized Theme.