You might not be able to. The router needs to support WDS and it must allow your device to connect using WDS. If this is true you could use one of the common "wifi extenders" better called a repeater. It is not optimum because you will lose at least 50% of the speed but when you have no other options it will work.
If it does not support WDS things get very messy. You would in effect have to build you own repeater that actually has a wifi bridge connected to a router wan port.
You could also look at ubiquiti wifi bridge devices since these can run as routers that have the wan as the wifi but they do no provide wifi on the lan so you would have to attach a AP to it to get wifi.