A universal instantiation means for each and every entity $c$ in the domain we have a correct inference rule of the form: $$\boxed {\begin{array}{c}\underline{\forall xP(x)} \\P(c)\end{array}}$$
For example,
By universal instantiation, given the premise , we may derive the conclusion , where is any object in the domain:
If holds for all the elements of the domain, it holds in particular for the element as well. Universal instantiation can be seen as -elimination.