Cascading routers

I have a SMC broadband router (smc7004vbr-ca) It has 4 ports but 5 computers need to connect to the internet. I also have this spare USR 8054 broadband wireless G router which also has 4 ports. I was wonderng if it would be possible to use either one of them as a switch in order to expand my network in order to allow the 5th computer to have internet access. Also I would need a little guidance as to how to use and protect my wireless network with the USR 8054 when I’ll have a laptop with a WLAN card.