When you attempt to go to enable mode are you prompted for a password?

If you are you prompted then need to do a password recovery if you don't know your password.

Password recover link below:

http://www.cisco.com/en/US/products/hw/routers/ps221/products_password_recovery09186a0080094773.shtml

You have created an enable password if you have already followed the guides below.

If you are not prompted for one but would like a password set you use the enable secret command

example

enable

config t

enable secret cisco

/end example

This will set a password of cisco for those trying to get into enable mode.

Here is a document on the enable secret command

http://www.cisco.com/en/US/tech/tk59/technologies_tech_note09186a00801d7efa.shtml#topic1

Here is a document to set the enable password. A little old 12.1, but still applies

http://www.cisco.com/en/US/docs/ios/12_1/security/command/reference/srdpass.html