I assume that you installed using the JEMS installer (since the zip file download does not secure the console). The installer asked for a user name and password on the page of the wizard where it asks about securing the console, so what user name and password did you give it? If you don't remember, try user name "admin" with no password. If that doesn't work, look at server/default/conf/props/*-users.properties, that has the user name and password in it.
Slight correction. The installer will not let you get passed the "secure consoles" page without entering in a password. You you must have entered something. What did you enter? If you can't remember, look in jmx-console-users.xml.