You will need to add a spline to your scene to see the deformation from that spline in your scene.
You can drag and drop a spline into the Spline link field.
This Flower spline has been dropped into the Spline Link field.
Alternatively, you can use the Eyedrop tool to select the spline, directly from the Object Manager.
Enabling this parameter re-samples the base spline, by uniformly distributing points along the spline.
If there is a low point count in the base spline and resample is turned off, there will be a stepped result.
Raising this slider adds more points to the resampled spline making it smoother.