what do i need to colonize new sector?

If you successfully invade a sector it automatically becomes a colony (you can have up to 3 colonies at a time, after this new invaded sectors won't become colonies).  You can select which sectors you want to be colonies when you have more than 3 in the colonies tab of your command center.  In this tab you can also collect resources from your colonies, and choose which resource you want the colony to generate.  A colony can store up to 12 hours worth of resources, and gains 25% of the sectors production in the chosen resource.