MOVEMENT and PORTAL and THERMAL are effects plugins - not a software instrument like most other Output products.

Install your Output Plugin directly from the Splice desktop client.

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 your Output plugin to and hit Start scan. The default installation path is:

C:\Program Files\VSTPlugins\