It depends on exactly which point in the Cold War you are talking about, because that limits their delivery possibilities. But in general, the main approach was going to be over the north pole, because that's the straight-line approach of a ballistic missile or a bomber. Which is to say, not from the East or West: it wasn't like a mercator map. Most intercontinental war maps from the Cold War are a polar projection for this reason. And this is also why the US put so much emphasis on polar-oriented early warning systems, especially early on when they anticipated a bomber threat.

The only east/west attacks would be from submarines, once the Soviets had those. Submarine-launched ballistic (and cruise) missiles open up the possibility of attacking from many different directions.

Worried about ballistic missile defenses and early warnings, the Soviets also invested in a system called FOBS (Fractional Orbital Bombardment System), which is essentially a weapon you put up as a satellite, in orbit, that can then come down wherever. They only appear to have deployed a few of these — a dozen or so — because they have many technical deficiencies.

I think it is perhaps worth emphasizing that for much of the Cold War, the largest Soviet salvo would have been in short- and intermediate-range missiles deployed against targets in Western Europe. Americans tend to ignore these but this was the easiest thing for the Soviets to threaten credibly, and a large part of their deterrence strategy — the US might not get as totally destroyed as the Soviet Union might (though by the 1970s, they were more or less at parity), but their allies would be burnt to cinders.