The Main Menu on the blackboard at the left of your Admiral's Office gives you access to all the main functions you will need to play a campaign turn in SAS.
You can bring up a briefing report at any time by clicking on "Briefings".
The report is a hyperlinked overview of the situation you face at the start of the turn, and will be useful background information for making decisions.
Click on "Build" when you are ready to start building key resources - ships, troops, infrastructure and aircraft (if aircraft are enabled for the current campaign). The Build Menu will appear, giving you access to each of these build functions.
Click on "Deploy" when you are ready to start deploying these resources. You obviously need to build them first!. The Deploy Menu will appear, giving you access to each of these deploy functions.
Click on "GO!" when (and only when!) you have finished all your build and deploy tasks and are ready to finish the turn and run the turn calculation.