stellaris
In Stellaris, strategic resources provide bonuses to your empire of various kinds. I know sometimes the resources are utilized in certain buildings, research or modules but I am not sure how the bonuses are applied.
If I have Neutronium Ore for example and looking in the strategic resources menu, it says +20% armor. Is that just automatically applied to all my ships? Is it only for new ones? Will it apply after an upgrade?
If you've already surveyed the system a new resource is in, then it shows up right away. If you've already built a mining station there, then you have access to it right away.
I can't find a good citation for these facts, but I've played the game for dozens of hours and can assure you that it is the case. I believe there's also an in-game tip to this effect.
At the top of the screen, to the right of your technology income, there is a white diamond-shaped icon.
Next to the icon are numbers representing how many total resources you have access to, and how many of those are currently available for use. Hovering over the icon shows you those same numbers, but for each individual type of resource. Thanks to @toolkitxx for pointing out the icon, and @Sjoerd for providing a picture.
When you are trying to build something that requires one of these strategic resources, a red X on the thing that you're trying to build indicates that you don't have the resource available in the same sector.
If you have a lot of influence to spare, you can always try sectoring the resource and using the "missing a resource" notification to find the object that was originally using it...
Best Answer
So it seems that strategic resources that provide bonuses to ships such as these are automatically applied.
When you hover over stats that would be affected by the resources, you can see it lists the bonus applied. This includes new and old ships.
When I hover over armor it says +20% which lines up with having the Neutronium.
Ones that are used for buildings are used up and go towards their construction.
Certain resources like Neutronium also automatically unlock new research like the level V armor.
I came across this forum that lists what determines resources showing up in systems generally speaking.