If the white spots are slightly raised and have a soft, cotton-like texture to them, they are mealybugs. If they are flat and lack texture, then it is probably pesticidal residue from the nursery and it can be wiped away with a bit of soap and water on a soft cloth.
If they are mealybugs, let us know so we can tell you how to treat them.
If you are unsure, then carefully wipe away all of the white stuff and monitor the fronds to see if any of it returns. If it does, then you know you have a pest problem.
The yellowed lower frond in unrelated. It is normal for older fronds to die back gradually as new growth is added on top.
If you post a photo that shows the entire Kentia, including its pot, we may identify some other issues. Give your Kentia lots of very bright indirect light and keep the soil moderately moist.
