@DFW_Mark 

All you would need to do is connect both extenders in AP mode to the router via Ethernet.   Keep in mind that the extenders themselves will be seperate APs, even if you assign the same SSID and password as your router uses you will still have 3 seperate APs in your network.  I would suggest a different SSID for each to ensure that your client devices do not have any connectivity issues.  

  @DFW_Mark 

I misunderstood what you were asking then.  You would then have to use RE mode to connect the range extenders to the source.  While in RE mode the ethernet port on the extenders is for client devices they do no provide POE nor is it recommended to connect one RE to the other, regardless of mode.  The connection rate and speed on the 2nd adapter would be to small to be effective. 

What you would need to do if you have the need for 2 extenders is setup one in RE mode to the router, then power it down and setup the 2nd one.  Then power up the frist one.  This would ensure that you do not daisy chain the extenders, which would reduce the effectivness of the 2nd extender.