I think I've understood the general idea of the WGC (proposed in https://arxiv.org/abs/hep-th/0601001). From a more recent review, I quote:
In a consistent effective field theory (EFT) coupled to gravity, gravity must always be the weakest force.
(The reference is https://arxiv.org/abs/1711.00864). This implies that in the theory there should be at least one charged particle for which we have $m\le M_p q$, where $m$ is the mass of the particle, $q$ is the charge and $M_p$ is the Planck mass. This is connected to a hidden ultraviolet scale beneath the Planck mass.
What I don't understand is how can we practically use this conjecture in the framework of the Swampland program. What should we do in the EFT? Should we search for a charged particle satisfying the mass-charge relation or do something with the new scale? Could you give me a simple example of application?