My lights and batteries all came for my DT3 and while I'm home for Easter break I thought I would try and hook them up.  So I looked at wiring diagrams (there isn't a wiring diagram for DT3 that I saw so i used DT250) and to be honest I have a hard time understanding some of it.  All of the diagrams show a fuse coming off the red of the battery and I do not see one there so maybe I need to buy one, I know I've read about a 6V regulator is that the same? I am also not doing blinkers just to note.  Any support would be awesome, I am very new to all of this. One last thing is that my headlight when I place it in the dome it sticks out a few inches, will the silver ring hold that in? I am missing that part I just realized. 

Have a look at the reply I have just posted under "Clear coating my tank" - this will get you started, and maybe even finished!

You will need to buy a 6v regulator and plug this into the blue in the headlight bucket - see the Service Bulletin in the Tech Library for precise fitting instructions. Don't turn your lights on before doing this, otherwise you might blow your nice new headlight!!

Edit - I'm pretty sure that there is a wiring diagram for the DT3 (same as the RT2/3 and DT2), although it might be tucked away in one of the Service Manuals. It will be a pretty basic diagram, though.

Thank you, to be clear I need a fuse and a 6v regulator for the light?  Also the wiring is all there from before so there is a chance there is already a 6v regulator in there although I don't know the last time there was a battery and lights in the bike.  Thanks for your help.

It's possible that a previous owner has fitted a regulator, but I would say unlikely. I have attached a couple of pictures of different Yamaha 6v regulators, so you know what to look out for.

If there is no fuse and holder present, you should have two spare female ended wires in the loom, together with one red male ended wire.

  

Not the same bike but fuse should look a bit like this.
I fitted the regulator on my CT1-C under the tank and extended the yellow wire to the headlight bucket where it connects to the blue as Alan said.