Yes, thin them out, mercilessly. Especially since this is a young tree. If not, you'll have substandard fruit this year and probably none next year. Try to keep the best looking, largest fruit in each cluster with the thickest stems. You may have to remove all fruits from some clusters if the clusters are too close together. Guidelines vary for how many fruits to keep. I try to keep 12" between any two apples, but I made that one up myself. Another one I've read is that there should be at least 30 leaves per apple. That's probably better since it accounts for uneven distribution throughout the tree.