How can I address gaps in the aluminum siding around my windows and above the shutters before installing new shutters to ensure proper insulation for the cold weather?

I’m in the process of changing out the shutters on my house, but the previous owners made some cuts in the aluminum siding above the old shutters. I’m wondering what I should do about the gaps between the sides of the windows and the siding, as well as where the siding was cut. I live in a cold climate, so I really want to make sure everything is well insulated. I plan to repaint the siding in the spring. Any suggestions on how to handle this situation?