How is your network setup. Please provide more info.
1.how the connections are done.
2.name and model of router, repeater.
3. what operating system is on your computer used to configure it
For setting up Wireless repeating, your router should have WDS [Wireless Distribution System] feature.
Assuming your router does have WDS, here is a small outline what has to be done.
1. Make note of wireless MAC address of router and wireless repeater, router's ip address and repeater's ip address.
2. Setup both router and repeater with same SSID, channel, security and password. [note: some brands only work with security type: None or WEP]
3. on router find the wireless repeating feature and select it and set it as wireless base station and type in the mac address of the Wireless repeater.
4. Go to the wireless repeater and find the option for wireless repeating and set it with mac address of router. you'll have to assign an ip for the repeater which is in the same range of your router.