OFX plugin is installed automatically on Windows system. On macOS please select Options / Install plugins…
If Premiere Pro / AE is open please restart it to reload the transmitter plugin.
Then please go to Preferences / Playback…
And make sure Nobe OmniScope Transmitter is enabled:
Once the configuration is complete you can now connect from OmniScope selecting Premiere Pro / AE in the Connect to dialog box.