i cant get the rocks hot how are you supost to do that please is this a glich in the game or am i crasy please if you know please help.

You need to have a fire started in the fire pit near the food bin. Then drop a villager on the rock pile near the bridge to the lab.

ok how do i lite the pit

Gather firewood and dry grass from the area just above the fire pit. Then drop a villager on the prepared fire pit.