This package should be really easy and straightforward to use. You only need to import the Easings namespace with :
using GameLibrary.Easings;
Then you can use any easing function directly in your C# script :
Easing.QuadraticEaseInOut(0.73f);
You can also use the Interpolate function, which is equivalent :
Easing.Interpolate(0.73f, Easing.Ease.QuadraticEaseInOut);
You can visualize the different easing functions that have been implemented in this repo with this website : easings.net.
Here is a preview :
