In that case, I would not try to assist any of the eggs, but just leave them alone and hope for the best. In another week or two, if none have hatched, try cracking the oldest egg to see what's inside (it will probably have hatched by then if it was going to, based on what you found inside the first one.)
No heat lamp. Just room temperature.
With wild chickens, the way it works is:
The hen lays an egg every day, and otherwise goes about her business ignoring the eggs. The eggs sit in the nest, at whatever temperature nature provides. After a while, where there is a big clutch of eggs, the hen goes broody and sits on them. All the eggs start to develop at the same time, so they all hatch at the same time. That makes it easier for the hen to take care of the chicks, because they are all the same age.
With domestic chickens, they don't always get the details right, and we usually manage things a bit. But storing the eggs at room temperature will keep them from developing, so they just sit there and wait until you're ready to put them under the hen. If you use a heat lamp, they could get warm enough to start to grow, and that's not what you want.
You can store eggs for at least a week before you put them under a hen or in an incubator. If you store the eggs for 2-3 weeks some will still be able to develop and hatch, but some will not. You typically get the best hatch rate if you store eggs for 1 week or less. It's a balancing act, trying not to store them too long but to build up a convenient-sized clutch.