Satellites revolving around the earth are in a balanced condition. Being in a circular orbit means that the path of the satellite is balanced by equal inward moving tendency due to the centripetal force as well as the outward moving tendency due to the inertia of direction.
When the satellite is at a height where resistance due to atmosphere cannot be neglected, its orbital speed starts to decrease and it loses some of its kinetic energy. Also, its tendency to move in a straight line decreases. So, it will be dominated by the centripetal force. As a result, it will have spiral motion towards the earth and ultimately, it will fall on to the earth.