Hook lead rope to halter and tie them up for brief periods to a stout post at head height so they don't tangle on rope. Only need 2 or 3 feet of lead with a quick release knot. Too long and they'll get wrapped up in rope, which is not pretty and they can get hurt.
They will pull back and fight a bit, but eventually learn to give in to the rope. Pulling away makes halter put pressure behind hears which is uncomfortable. They learn by giving in it relieves the pressure.
After a few sessions of being tied up, once they stop fighting it, try leading them. If they resist, keep applying more pressure until they move forward toward you and rope goes slack. Reward them by relieving the pressure. When they pull against you, can also teach to move forward by giving treats.
After all this, if still resist, tie them with long rope to truck or something and slowly pull them until they give in. Stand with the rope while someone drives so they think you're leading them, not the truck or tractor.
Good luck.