setup app

What else do you want to do? If you’re trying to create a single-room home theatre setup, have you added the Eras as surrounds and added the Sub to your Arc? Or do you want the Eras as two independent rooms? Or a stereo-pair in a single room? 
 

Just give us a few clues and we can try to help…

As surrounds I’ve added arc and sub to ap  have all of them in loung room

Add the speakers you’re using as surrounds to two separate rooms using the app to ‘add device’, then use the command in the app in the Arc’s room to add them as surrounds. 

Make sure your Era 300’s are not stereo paired.  They must be separate rooms (room names don’t matter, call them Barney and Fred if you want).  Then, add the two Era 300’s as surrounds:

https://support.sonos.com/en-us/article/add-surround-speakers-to-a-sonos-home-theater