Everyone's opinions may offer slightly. Really its simple. Just continue your cycle as you would have otherwise, just take the mature filter pad/sponge and shake it out in your water. Preferably near the filter intake. It should make the water really cloudy and introduce a lot of gunk into your perfectly clean tank. That funk contains millions of the bacteria you need, which will quicker seed in your filter and speed up your cycle.
if the filter pad or sponge fits your filter, you could also just place it straight in and leave it. Either way just continue with your cycle as advised and it should complete very quickly.