My main router is an Archer C7. I recently acquired an Archer C6 with the hopes to daisy chain it to the C7 and use the C6 on a separate floor. How exactly do I do that?

My original router, connected to my ISP's modem is an Archer C7 on the main floor. Its wifi signal can only go so far downstairs due to a concrete floor so I picked up an Archer C50 to place...