How to mount a Sigma lens to a Nikon camera?

Lens is the Sigma Zoom II 1:3.5~85mm multicoated.
Camera is the Nikon F2 Photomic.

Go to a camera store

Exactly the same way you mount any other lens to the camera.
Just ensure it is the right fit.

Check the manual http://www.butkus.org/chinon/nikon/nikon_f2_photomic/nikon_f2_photomic.htm

You can only mount a Sigma lens with a Nikon Mount on a Nikon Camera. It is important to make sure the Sigma lens you buy does indeed have a Nikon Mount.

You need to buy a Sigma lens that has a Nikon mount or if it's for a lens oyu already have then you'll need an adapter to convert it from whatever lens mount it's currently at to Nikon but by doing so you'll lose through the lens metering, auto focus…