Capture One's Lens Cast Calibration (LCC) tool requires a "characterization" image to be captured alongside the image to be corrected. Simply capture your image in the studio or on location, followed quickly by a second image with an LCC plate held in the optical path like a filter.
In some specific cases, such as when working with a copy stand where you have fixed lighting and short working distances, you can substitute the LCC plate with a gray card. Make sure the card covers the complete field of view and that no part of the resulting image is close to being clipped in the highlights.
This second characterization image is used later in Capture One to create an LCC reference image and associated LCC profile. The success of the resultant LCC profile is dependent upon the angle of the incident light falling upon the sensor being as close as possible between the characterization image and that of the image you are trying to correct.
For optimal correction, it is worth avoiding lighting changes and not altering lens settings such as focus distance and aperture or applying any tilt and shift movements between the two images. When more generalized corrections are required, however, Capture One’s LCC tool is still capable of building highly-effective profiles.