How do we align a weapon's reticle to the centre of the screen when aiming?

When someone aims in a FPS, we see that the weapon’s reticle or iron sights always align with the centre of the screen (the crosshair). I have no idea on how to approach doing this, I can do it by moving the character holding the gun inside of the character blueprint but it takes a long time and it doesn’t work for every gun. Plus, I still don’t get the proper weapon view.

Essentially, I just want to know a way to do this:

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