The events during the mitosis happen continuously and are conventionally divided into four or five subphases (not every source treats the prometaphase as distinct phase).
The condensation of the replicated chromosomes is the first sign that a cell enters into the prophase and into mitosis. Those are first visible as thin threads within the nucleus. The miotic spindle apparatus forms outside of the nucleus between the two centrosomes that separate themselves and begin to move towards opposite poles of the cell.
The chromosomes arrange themselves in the equatorial plane of the spindle.
New nuclear membranes form around each of chromosome sets and build two daughter nuclei.