Confirm that your email address with Splice is correctly tied to an email address you can login to

From the Splice Desktop App install Arturia Software Center

If you're not seeing Arturia Software Center in the Apps & Plugins section of the Splice app, log out and back into the Splice app

Check your email for a message from Arturia to setup your Arturia account

Log in to the Arturia Software Center and install the Arturia plugin

Once signed into Arturia Software Center, you must “activate” the Arturia plugin. To do so click on the “Activate” button.

Sync button on Arturia Software Center will retrieve any updated license info from your Arturia account.

Restart your machine

Once installed navigate to FL Studio go to:

Options
General
Manage Plugins

On the left, you can add plugin search paths, add the location you installed the Arturia plugin into and hit Start scan.