fertilizers usually get tilled or mixed in with the dirt, you can add plant food like fox farm or miracle grow wich you just add to water appropriatly.
like the above person said, start with a 1/4 dose (it might seems like a tiny amount) and then if they do well for a couple feedings at that dosage you can increase the dosage to 1/2, i wouldnt increase the dosage any more than 1/4 of the original recomended dosage at a time and you should stay at the same dosage for a few feeding before you increase it again.
plant food or nutes as they like to call them does the same thing as a fertilizer the only difference is the fertilizer is used before planting and generally expected to last throughout the growing season,
i.e most big farms fertilize thier cornfields with cow manure, they rototill it into the ground then plant thier crops and do not ever feed them any plant foods, the fertilizer maintains nutrients for the plant for the whole season.
with plant food, it is super concentrated and already broken down into a form the plant can use so you cant just give a large dose and not have to feed them again you will kill them
from what i read MJ will utilize almost anything you feed them (plant food wise) as long as you dose them correctly and increase the dosing realisticly.
during the veg stage you plant will want a food that is higher in Nitrogen because that is the element plants use to produce green vegatation.
during the flowering stage you need P&K (potassium and Phosforus) and little to no nitrogen anymore so you will want to pick up 2 different kinds of food.
on the plant food package you should see a number that looks similar to this 10-10-10. The numbers stand for the percentage by weight of the three largest amount of elements or chemical compounds found in the fertilizer. The first number stands for Nitrogen. Nitrogen is important for making chlorophyll. This is the green pigment that plants use to make sugars. The second number stand for Phosphate (P2O5). This is important for flower production. If the second number is high it should help the plant bloom. The third number stand for Potash or Potassium (K20). This helps in root production.
hope this helps
-Brute-