As for PC/Laptop click on the wifi icon bottom right. I use one extender and shows which wifi connection it's connected to. This laptop is connected directly to the router -
With iphone go to settings and wifi. I don't know if more than 1 extender will be identified by a different number or not as I only use the one. As for TV I guess there mus be a setting for wifi but I'm using an ethernet cable on mine so can't help there.