You can tap into a vac feed with a "t" piece, but most likelas said one at base of carb somewhere.
What carb is it ?, ford fitted VV, 28/32 TLDM, 32DFT(xr3).
You can use a vacuum source from the inlet also, so long as it gets a feed, it is just for advancing the timing on cruise conditions to save fuel give better emmisions.
It will work ok without it but be a lot better smoother with it.
tabetha