Until the sword establishes- which takes a couple of weeks, do not add ferts to the gravel as it can burn the new roots trying to develop. Plants love the stuff you normally vacuum out of a non planted tank, for them it is food. Do not vacuum around the base of the plant.
Assuming the plant came with some root mass, you should be able to plant it so that it stays in the sand. Divide the roots into two bunches sort of like an inverted /\. Then create a decent sized hole that mounds in the center like similar /\- drape one bunch of roots on either side of the mound and allow the base of the plant to sit atop the /\. Then cover it all up. If needed place a small rock on the sand above each root grouping to help hold it down.