"you shall put this night's great business into my dispatch"

Definition: Please see notes below.

Notes: i.e., you shall leave the murder of the king to me.
This line is further evidence to support the theory that Lady Macbeth intends to commit Duncan's murder herself. Modern readers might take the word 'dispatch' to mean 'manage', in that Lady Macbeth is simply overseeing the murderous plan. However, in Elizabethan England, the word would have had only one meaning - 'to kill with quick efficiency.' Thus, Lady Macbeth prepares to slay Duncan while her husband plays the gentle host.