If you're asking just what you need for the physical connection,
Just use a
CAT5E or
CAT6 cable to connect one directly to the other.
If you're asking the entire process involved,
Presuming that your primary access point, device that will handle DHCP, is the wired router,
You will need to make the wireless router into a secondary access point.
First step is to verify that the wireless router even has the capability to act as a secondary access point
since not all can function as such.
You can check the wireless router manufacturer's website to see if it can function as such.
For some general idea of configuring a wireless router into a secondary access point,
You can take a look at the following tutorial/link,
If you have not purchased a wireless router already,
You can just purchase a wireless access point, to avoid configuration headache.