New Hose Bibb hard to turn

These are easy to take apart and inspect. First shut the water off (sounds like you already figured out that part). Put an open end wrench or adjustable straight-sided wrench on the big nut, called a packing nut, and counterclockwise to remove. Should not be very tight but be careful anyway, do not want to damage the soft brass nut. Carefully remove nut and the valve stem. At the bottom of the stem should be a small disc and attached to that disc a round rubber washer with a screw. This should be smooth and undamaged. Look down into the faucet and you will see a round flat area machined into the brass, this is the valve seat and will match the rubber washer, this should be smooth and undamaged also.

Look at the stem just under the packing nut. Probably have a rubber washer, likely somewhat cone shaped. This is called the packing washer. You can slide this up and down the stem a little bit, should be close fitting, the stem should be perfectly round and smooth, and the packing washer should be round and smooth and should fit nicely into the top of the faucet which should also be round and smooth.

If any of these parts are not fitting together nicely, or any kind of damage, that could be causing your problem. An internal manufacturing error is cause for getting an exchange.

To reassemble put the stem assembly back into the faucet and hand thread the packing nut so you know the threads are properly aligned. Use the wrench and tighten just a little, maybe 1/2 turn, does not need much force. Turn the valve handle to insure it turns, then close it all the way. Turn on the water supply. Check the valve function, should turn freely but with a little bit of resistance. If a bit of water seeps out between the stem and the packing nut then tighten the packing nut a little, maybe 1/8 of a turn. The packing nut squeezes the rubber packing washer around the valve stem. The goal is to get the packing nut just tight enough to prevent water from coming through the stem but no tighter -- too tight and there is too much friction to turn the valve.

If still not functioning well, perhaps there is some manufacturing problem not visible to the eye. May just have to exchange it.

Personally, I just changed 2 old hose valves on a house I bought, and put in stainless steel full flow ball valves. Gives much better water flow and should last practically forever.