Why are my pictures blury?

Okay so I just got a rokinon 14mm f/2.8 lens for my Nikon d3300 and all the pictures I've taken with it have come out blury. It's definitely the lens because my basic 18-55mm lens takes crystal clear pics. I've been testing it by taking pictures of trees about 250ft away. Is there settings I need to adjust my camera to for this lens? I've just been using auto focus but I can't get it to focus right. Is my subject too close and that s why they re blury? Because this lens is usually used to take pictures of the sky and stars. Or is it a problem with the lens on an inside piece of glass that I wouldn t be able to clean without taking it apart?

Which did you buy, the one with the AE chip (auto-exposure).

Hopefully you did, so you can use your camera's lightmeter to get the right exposure. That lens however is NOT an auto-focus lens, that is why it costs less than $400. You must use the electronic rangefinder in the camera's viewfinder to get good focus.

For clarity, "blur" is caused by camera or subject movement during longer exposures (1/125th second or longer). What you are describing is an out of focus image.

NEW lenses do NOT need to be cleaned at all, especially if you place a NC or UV filter on it to protect the lenses front element from sticky fingers, flying mud or other debris.

In the future, when you buy another lens, make sure that it has an auto-focus motor in it so that it will auto-focus on your camera

That's a wide angle lens. Minimum focusing distance is less than a foot. Trees 250 feet away should come out clear easily. Wide angle lenses have very long DOF.

There's nothing to set, except maybe for your camera's diopter, to make sure you see the way the camera sees.

You may be correct thinking it's an internal problem with the optics. If this lens is new, have it exchanged. If it's secondhand return for a refund.

So when you could get no photos in focus, it honestly never occurred to you to MANUALLY focus the lens? Bottom line, you bought the wrong lens for your camera if you want auto focus.