In essence, you just put up catenary/trolley wire (or if your prototype/ambition lies that way, lay third-rail track) and run electric prototype trains. There is, or was at one time, an "electric" rule where you designated a powerhouse and had to deliver coal to it or everything stopped, but that is optional and, probably, obsolete.
Third rail is not as easy as it sounds: to do it up right, you should use the version of your track type without third rail through points/switches. But overhead wire, either catenary or trolley, is a considerable undertaking since it's up to you to make it follow the tracks and maintain a uniform height. Good luck!