To directly answer your request for the steps:

1. Put camera in manual (M) mode on the top dial
2. Adjust ALL settings (shutter, ISO, aperture, focus) manually as needed
3. Shoot
4. "Git Gud" at manual mode

As mentioned in another answer: The lens is likely manual and the adapter is only a mechanical adapter, to make it physically connect, but there is no logical connection to the chip on the lens (if there is one), so the camera cannot detect it. Put it in manual mode and you should be able to shoot.

For information's sake: The micro-chips (or "CPU"s) in lenses report and allow control of the aperture and focus on the lens by the camera body. If the body doesn't know the aperture and can't control focus, it can't automatically create the ideal exposure. On your camera, that's the end of the story and it basically says "I can't do this" by saying it doesn't detect a lens.

Note that some higher end cameras might allow other modes besides manual with a manual lens if they can meter with the stops down ("stop-down metering"). Our D3XXX series cameras (I have a D3400) don't seem to have that :(, so ISO and shutter must be adjusted for every environment.

Some other things to be aware of:

1. If your D3300 is anything like my D3400 in this case (guessing it's the same) you won't have any metering capability, which means no auto-focus, and no auto-exposure. Set the shutter and ISO on the camera, and the f-stop and focus on the lens, all manually.
2. There is an easy way to "conveniently" adjust shutter and ISO on this model: by default the thumb wheel (top-right above the LCD) is the shutter speed, and there is an 'Fn' button on the front of the body left of the lens, under the flash control button. In M mode, while you hold this the thumb-wheel adjusts ISO. So you can quickly adjust both with your thumb, then focus and shoot.