It depends on the electrodes geometry Id say. One application I worked with was based on two coils - for transmitting through the skull bone. One coil - placed outside the body - was excited with a discrete port, the other had a resistance attached to it which monitored the transferred voltage.

It seems your case is an electrode, so you very likely connect the external part to a discrete port, which might in turn be either 50 Ohm (and later in Design Studio you assign it to the desired pulse, using a Transient Task) or use directly the pulse as a signal reference, in the transient (time) solver. Inside the head that would be connected to a load, similar to the one thats actually used. You'll then see the power transfer by watching the voltages and currents.

thank you Marselo