Because the soil you are using is mostly sand, I would recommend using more nitrogen than I otherwise would. I am assuming (because you know the ingredient ratio of the growing media) that it's in a pot. Use something like a 12-8-8 fertilizer every two weeks while the tree is growing. Do not fertilize during dormant periods. Norfolk Island Pines aren't too picky fertilizer-wise, and many people use 10-10-10 with okay results.
Do not spray it on the foliage, because these trees do not take it in very efficiently, and fertilizer residue could build up, slowing photosynthesis, eventually killing the tree.
Use it as a root drench every 2 weeks when you water. This will be the most efficient way to apply it, and also spread the fertilizer evenly through the root system, so you don't burn the feeder roots.