1. Download the module (klaviyo-x.x.x.ocmod.zip) as per your opencart version
2. Login to admin
3. Go to Extension > Installer.
4. Upload klaviyo-x.x.x.ocmod.zip
5. Go to your Extensions > Extension > Modules or Extension > Modules
6. Find Klaviyo in your modules list.
7. Click on Install button
8. Click edit button
9. Save the API KEY value and Enable the module and Click Save
10. You are done.

The last thing to do with your OpenCart install is copy and paste the a PHP code at the end of the index.php file, right before the

line. You will need to access your index.php file via filezilla or your file manager.

You can find this code in the readme.txt file of your download (klaviyo-opencart-21xx.zip/readme.txt)

You can get free installation support from https://www.huntbee.com/get-support