In order to collect from a Resource Town or Village, your own or allied city will need to control it. To control a Resource Town, you must first send your Legion to the Resource Town.
To send your Legion to a town, you must click on the legion in your city, and select the icon with the four arrows, then select the icon with the compass to send the legion to the Empire Map. On the Empire Map you must then select your legion and choose the icon with the four arrows to move the legion. You will then see another series of icons, select the icon with the walking feet to move the legion to a specific area. You will then be asked if you want to send the legion as an attacker or a defender. To capture a town with Imperial Points, it must be sent as an attacker. After the legion arrives, you will be able to spend your Imperial Points to claim the area.
Once the Resource Town or Village is captured and controlled by you or an allied city, you can freely send Foragers to the location to collect. If a City aligned to an opposing house takes control of the location, you will no longer be able to send Foragers as the location no longer belongs to you.