Missions in Age of Wonders: Planetfall takes place on different maps made up of multiple sectors. If you want to grow in power, you will need to annex and exploit nearby sectors to use the resources they contain. This will allow you to grow your colonies, and support them through various agricultural, industrial, and military means.
How To Annex A Sector
To annex a sector, you must first ensure there are no enemies in it. If the sector contains an enemy army, you must defeat it before you can annex the sector. Once the sector is clear, you can move an army to the central hex of the sector. This will have a glowing yellow marker on it. When you arrive on that hex, you will get multiple options, one of which will be to annex the sector for a nearby colony. Doing so will add the territory to the colonies, allows you to build upon it, and exploit it, adding to your various income streams. You will need to ensure that you have enough food to support the new sector. This is less of an issue if the sector you are annexing has a good source of food.
How To Exploit A Sector
Once a sector has been annexed, you can exploit it. Different sectors will have different features and attributes that will produce different resources. You will be able to exploit the sector for Energy, Agriculture, Industry, or Research. It is always best to carefully examine the details of the sector by clicking on it, then choose what type of exploitation you wish to do. To exploit the sector, you will need to click on the colony it is annexed by. Click on the Sector Production tab shown above, then choose the exploitation type you wish to do, then click on Produce.
Now you have annexed the sector, and are exploiting it for the resource that you need, remember that you can exploit and annex multiple sectors for each of your colonies. Keep in mind; there is also a limit on how much of each type of exploitation your colonies can do, so make sure you annex sectors into colonies that need the type of resources you can exploit from them.