Once you've assigned all your characters to a Takeover and the "Preparation for Combat" timer has completed, you can start the Combat sequence. You can fight manually by selecting a crew member and tapping on the enemy you want to attack, or you can choose the "Auto Combat" option to make the fighting automatic.

At any time you can choose to "skip" the Combat and go directly to the result screen.

To successfully complete a Takeover, you need at least one assigned character to have survived the Combat.