Most Yucca plants will produce offsets (sideshoots) often from the base of the plant. These will often have small roots near the base especially if the shoot emerged from under the soil. These can be seperated with a sharp knife as close to the mother plant as possible. Don't overwater at first!
In the unlikely event of seed pods developing on a lone plant (most types I beleive are self sterile) and assuming the seed is viable, the seed pod should split open naturally to release the seeds which can then be sown in a suitable seed compost in a propagator.