This has been extensively studied for years, with one of the earliest studies being Project Thor, which Jerry Pournelle has written about from time to time, being one of the investigators of the system.
Like most "smart" weapons, the Thor projectiles have a sensor in the nose, and some aerodynamic surfaces (Pournelle called them "tabs") which are under the control of a guidance mechanism in the weapon. Since "Thor" projectiles were "flying crowbars" made of a dense material like Tungsten, you could consider them to be overgrown variants of the Armour Piercing Discarding Sabot Fins Stabilized projectiles fired from tanks (APDSFS).
So we have a long, slender "dart" with a few differences: the sharp tip is covered with a thimble shaped cap made of some heat resistant material, and the fins are very much smaller than usual (since this will be diving into the Earth's atmosphere at @ Mach 25, large fins are going to be counter productive).
For your question, the Thor would be directed towards advancing Soviet tank columns or surface warships much the same way anything else would, some observer reports the target, provides the location and call for fire. The Space Fire Control officer confirms the target coordinates and passes it electronically to the satellite, which fires it's retrorockets and reenters the atmosphere, releasing the Thor submunitions. It is pointed in the correct direction and will reach the target box very shortly. If you are just looking for a cheap and dirty solution, you can stop right there, each individual projectile will impact with the force of a 250lb HE bomb, and provided you have enough packed in the satellite, you can plough the ground much like Soviet or Russian rocket artillery.
Pournelle was after a much more elegant solution. Spending millions of dollars to launch a satellite to simply provide area fire was far too expensive for the effect you would get. Once the satellite had been given instructions to deorbit, it would be arriving inside the "target box" and the submunitions would all be inside a defined boundary where the target was identified. In Pournelle's vision, once the reentry period passed, the heat resistant nose caps would be ejected and the seeker heads would look for the targets on their own, using millimetric radar or some form of thermal imagery to strike individual tanks or plunge through the upper decks of Soviet warships. Realistically, even in the 1980's this would be straining contemporary technology, so many of the Thor's would probably be fitted with laser seekers, and on the ground or aerial spotters would use laser designators to mark the targets, and the Thor's wold make corrections using their small "tabs" to home in on the target. Helicopters like the Apache and the various scout helicopters, as well as A-10 Thunderbolts and other FAC airplanes would all make excellent markers against Soviet land forces, while the Navy would have to make due with laser targeting pods on F-18's or Seahawk helicopters in this time period.
Today of course, a greater portion of the Thor's would be smart or even brilliant, capable of seeking their own targets, while drones and UAV's would do much of the target marking for laser seekers. We should also expect that a multitude of different mechanisms would be used, so only a small portion of the Thor projectiles could be spoofed or otherwise misdirected from their targets. In the end, a soldier on the ground still has to see the targets and identify their location to define the target box for these smart and brilliant weapons to work.