How do you activate Ammo upgrades?
 

Once you supply yourself with a bunch of Ammo upgrades which I have so far.

How do you activate the items or select the items if you want to use them?
I know about your invatory bar and how to view everything you have. But I don't know how to activate or select the items on your items list like an upgrade or stronger stamina. How do you do that?

If its in your inventory, it applies the upgrade itself.

You have to buy the upgraded ammo itself. Then when you capture something of that upgrade type, (i.e. capture a chippunk but have Howler Punk upgrade) the ammo you hunted will automatically upgrade.

And stamina upgrades are automatic as well.