You need some basic networking knowledge to follow these steps. Since you have connected it to your wireless network you can use the web-based configuration utility.

The default IP address of the SMC2655W is 192.168.2.50. If you prefer to con-
figure the AP via a web browser rather than the utility program, you can do so
by opening your web browser and going to
"http://192.168.2.50". You need to be sure that your computer is configured in
the same subnet in order to access the Access Point's web management inter-
face. For example, your machine's IP should be 192.168.2.x (where x is not
equal to one (1) or fifty (50), but is less than 255).
Once you are able to access the AP, you will need to login by entering the
default password. Type in "default" and then press [Login].

Once you are logged in, you will be able to view the firmware version, change
the IP scheme, change the password and/or configure
security options.

Click the [Configuration] link on the left and a drop down menu will appear on
the page. Then click the [General] option to continue. The "Access Point
Name" is simply used to identify the AP. This is not the Service Set Identifier.
The "ESSID" field represents the wireless workgroup name. Your wireless
clients must have the same value configured in their network settings. You can
also choose the operating radio channel. In the "Administration Parameters"
section, you can change the password required for any administrator to log into
this AP. Note that this password is needed to login via both the web interface
and the utility application. After changing any parameters, you need to press
the [Apply] button on the bottom of the page.

Click the [WEP] link on the left in order to access the 64/128-bit encryption
configuration.
For HEX (0-9, A-F) "Key Format", the security is enabled by entering 10-digit
keys for the 64-bit WEP configuration, and 26-digit keys for a 128-bit WEP con-
figuration. Be sure to type "0x" before entering the HEX key. For ASCII "Key
Format", the security is enabled by entering 5-letter keys for 64-bit WEP, and
13-letter keys for 128-bit WEP.
Note that there are 4 different keys to choose from. Choose the Key that has
the encryption string you prefer. The wireless clients must be configured in this
same fashion.

Here is the manual for future reference. The web based configuration utility starts at page 18.

By the way the default administrator password is: default
You may want to change that one too.

Good luck!

U will have to log into the router look at the documentation that came with the router

To secure your wireless network from unauthorized access,please click on this link and follow my instructions :- http://www.fixya.com/support/r3559128-wireless_router_security