wireless extension of wired network

Hi,
I have a Level1 router with dhcp and printer server and build-in adsl modem
(fbr-1407a) and 4 network connections (3 used). I would like to extend the
network wirelessly. How can I accomplish this? I'm told this can be achieved
with an Access Point attached to the router.
Someone any info about this or where to find it? (models, configuration of
ip's, dhcp ...)?
Thanks!