Nikon t mount

I have a Nikon d3300 and recently bought a telephoto lens which required a tmount. It says no lens attached and I know it's because I have to set things to manual. What do I need to switch and how?

The reason it says no lens is because there is no electric signal from the lens for it to recognise,how or what you do i have no idea.

Welcome to the forum

I think if you can release the shutter, you are good to go. My old d3100 will release the shutter in manual mode even without a lens installed. Set the aperture on the lens, set manual release mode on camera, set the shutter speed on the camera and it should go. No metering though.