It is difficult to answer with specifics without knowing your particular circumstance but you can think of a few ways you might use EMS to expand on your training.
One might be to “superset” during the hypertrophy phase. Supersets, where you go up to your max working weight and then go downwards in sets as far as possible, were very popular years ago as they increase capacity quickly- but often at the expense of longer term gain due to CNS overload. A compromise can be hypertrophy weights at top working weights and then EMS after. The standard thinking is to wait 4 hours after the last workout session but it might be interesting to go immediately after with the muscles you want to superset. I haven’t tried that yet as I like to stick closely to what I know works unless I am stuck in an unusual situation, like a longer term injury etc.
If you think this way, you would prob follow the same pattern of work distribution as your weight exercises. You can see the early weight phase set-up in the GPP download for a guide, stimming muscle groups on the days they are worked. This would move you progressively from every traing day to every other day by the late GPP stage.
I would recommend a period away from the EMS before using it in the second portion of each max strength block as shown in the CFTS model (on weights day, occuring every other day at this point).
Thoughts?