I have Asus DSL-N10E Wireless-N150 ADSL Modem Router. I just want to use it as a wireless router, as my connection comes through RJ-45 (lan) cable.
How can this be done?
You probably can't easily do this - assuming you have a single RJ-45 cable and are trying to share multiple accounts off it. There are 2 ways this can technically be done - (1) By getting a DSLAM to convert Ethernet to ADSL - but this is way more expensive, complex and slower then just getting a new router or (b) If your router partially supports it loading OpenWRT or similar onto it and configuring a LAN port as a WAN port. Having done this as part of a complex custom solution for my job as an Infrastructure Engineer , I'd honestly say that its not worth the difficulties - even if it can be done. (Its not intuitive at all, and assumes a good knowledge of Linux, Bridging and VLANS - and thats only if OpenWRT will work on your router - which is probably untested because last I looked it did not support ADSL - so people are unlikely to have spent time on the remaining functionality it has)
If, on the other hand the RJ-45 (lan) cable will allow you to have many connections, and you trust the provider as they can see your lan, you can set up the router as an Access Point rather then a wireless router. I've not used that specific one, but done this with quite a few routers. The general idea is to plug the WIFI router into on the LAN interface to the switch feeding the rest of your network. You will also need to disable DHCP, and will probably want to assign a static IP address for the LAN interface (which should, of-course, be in the range assigned to your LAN by your provider)