The shape in the wavetable can be thought of as something like a formant envelope; it remains fixed even when you shift the frequency of the fundamental and the spacing of the partials under that envelope.
The beginning of the wavetable corresponds to a frequency of 0 hz and the end of the table corresponds to a frequency of half the sampling rate. The spectral shape acts something like a fixed filter or formant characteristic, attenuating the amplitudes of some frequencies more than others.
The value in the Frequency field is used to look into this table (somewhere in the range of 0 hz at the left edge of the wavetable to half the sample rate at the right edge of the table). The amplitude at that point in the table becomes the amplitude of that frequency in the OscillatorBank or other generator bank that is controlled by this spectral source. The frequencies of the other partials are: Frequency + (partialNumber * Spacing). For example, if you set the Spacing parameter to the fundamental frequency, the partials will be harmonics of the value in Frequency. You can use smaller or larger values in Spacing to get nonharmonic partials.
The OscillatorBank and other generator banks do not expect negative amplitudes so it would be best to avoid those in your spectral shapes.