How did Scrooge get rid of the ghost?
The only ghost Scrooge attempts to vanquish is the Ghost of Christmas Past, and he attempts to get rid of it by placing the "extinguisher" over the top of it and pressing it down to the ground, "but though Scrooge pressed it down with all his force, he could not hide the light; which streamed from under it." This image of Scrooge pressing down on the Ghost of Christmas Past clearly reveals that it is made up of light, and in this case light symbolizes the truth, which Scrooge does not want to see as revealed in his actions of trying to extinguish it, but hard as he tries, he cannot conceal the truth.
After Scrooge is successful in getting rid of the Ghost of Christmas Past, he is overcome with "an irresistible drowsiness" and falls to sleep. The sleepiness is indicative of the incredible release of emotions Scrooge experiences when he witnesses the truth of his past.