Like mini lathes, a lot of these machines differ only in their paint job and sticker name.
I have found that the US-supplied versions (JET, Grizzley, etc.) seem to have better manuals than our own.
Avail yourself of a list of likely manufacturers and then put 'xxx turret mill' into Google and look at images, where 'xxx' is the manufacturer name. That will help you find the model designation that manufacturer uses.
An original Bridgeport manual might also give you some pointers as the machines are close copies.
If you can find a suitable exploded diagram of the machine, that can help a lot with finding where to poke your oil gun.
Have a look at page 29. of this:
https://content.jettools.com/assets/manuals/690182_man_EN.pdf
Item 142 is the quill and it looks like half way up it is a drilling for an oil nipple, possibly for the lower spindle bearings.
If you lower the quill and smear with oil, it will come off the first time you retract the quill. Maybe lower it a little and introduce a thin oil from the top – it will be ground steel slowly sliding in cast iron so does not need much.