The resonant frequency of an antenna may be increased by:

Frequency and wavelength have an inverse relationship. Higher frequencies have shorter wavelengths. Therefore, to make an antenna resonate at a higher frequency, you must physically shorten the radiating element to match the shorter wavelength. Lengthening the radiating element would do the exact opposite, causing the antenna to resonate at a lower frequency. Changing the height of the antenna above ground primarily affects the radiation pattern (take-off angle) and the feedpoint impedance, not the fundamental resonant frequency of the wire itself.