OC 4.1.0.3 paypal integration

On the extensions page, payments, there is a down arrow to download "PayPal Checkout Integration"

I have logged off and back on, and each time I try it from this page it says "Signature hash does not match!" (in Red)

Appears I need to enter an API key somewhere.

So I went to System/User/API, and I have an API key #.

Where do I add this?

-----------------------------------------------alternate way tried----------------------------------------------

So I tried downloading version 4+ of this extension from "PayPal Checkout Integration" on opencart.com extensions page.

OCMOD version, I went to INSTALLER, UPLOADED it, it then lists it on the list of installed extensions.

But it is partially grayed out at the bottom of this list.

I clicked the EDIT button and it just pops up a box with no way of addressing anything.

On the MODIFICATION PAGE: I tried CLEARING and REFRESHING to no avail.


What am I missing? THANK YOU