Ground Wires for Turntables

The ground wire is part of the cord coming out of the turntable (i.e. there should be two RCA plugs and a spade connector) the spade connector is the ground that you attach to your phono stage or pre-amp. It may sound better with or without the ground so try it both ways. Page 7 of the DP-29F manual is pretty clear in this regard.
https://www.manualslib.com/manual/38508/Denon-Dp-29f.html?page=7#manual

If the wire is there the simply strip it bare and tighten that down under the earth point on your amp. If there’s no wire then you could simply run a wire from the table (usually under a screw on the back say) to your amp ground but if you don’t have any issues without it then don’t bother. Five times out of ten in my systems cartridges sound better with the ground floating, every cart and phono stage will be different