To change the tuning of a preset in Equator, simply go to the Global tab, and below Preset Master adjust the Fine tuning knob. This knob displays the difference in cents from A=440Hz. If you'd like to adjust the preset to a tuning different from A=440Hz, first look up the difference in cents and then adjust the Equator preset accordingly.
For example, to change a preset to A=432Hz, we can look up the difference in cents from A=440Hz. This is between -31 and -32 cents, so we can simply adjust the the preset's Fine tuning to -31 or -32.
The tuning is saved with each preset individually, so if you'd like to use several presets at a different tuning you'll want to adjust the tuning of each preset and save each preset with this tuning.