Hello everyone

After failing my first shard and conquering the second one I sarted the third shard and I ran into a province with a red iron icon. The second shard had a province with a regular iron icon, from what I understand that increases income and it makes all units and buildings that need iron cheaper, is that right? In this case however, the buildings and troops were not cheaper. First I thought that I had to discover the iron, so I kept exploring the province until I reached 100%, but the icon still remains red. What do I need to do to get to the iron?

How stupid of me -.- Thank you. (for anyone who finds this in the future, you need to select the iron deposit among the locations as the location to enter; in my case it was held ny a group of orcs)