after newly installing jboss you have to create users in order to login to admin console and do some admin things.
usually in JBoss users are of two types :
1.Management Realm (server administrators)
2.Application Realm (application users)
to add users issue following command:
<JBoss_Home>\bin\add-user.bat
which looks like as shown :
after you add user then once if you open the admin console you will be prompted with user name & password as shown:
Happy Learning!
understandingjboss 