To define an User to RACF you have to execute the following command:

CONNECT USERIDxx  GROUP(JAZADMNS)   

 Of course, you have to perform and define other resurces ( ADDGROUP,RDEFINE,  PROFILES, .... )  before to CONNECT the RACF USERID. 

RACF is strogly related with TSO ..... and you have to consider also other definitions (ALIAS , etc.. ) within the TSO.

First of all you have to define a PROFILE under RACF to define your USERID.

It means that the USERID  rules are also related to  RACF  .... but not only.

You have t define the RACF segment of a user profile using the ADDUSER command, or the RACF ISPF panels.  Start by identifying RACF administrative units for the users. For example, you could consider all users who have the same manager, or all users within an order entry function, an administrative unit. RACF handles these units as groups of individual users who have similar requirements for access  system resources.

The ADDUSER sintax is :

 [subsystem-prefix]{ADDUSER | AU}   (userid ...)   [ ADDCATEGORY(category-name ...) ]   [ ADSP | NOADSP ]   [ AT([node].userid ...) | ONLYAT([node].userid ...) ]   [ AUDITOR | NOAUDITOR ]   [ AUTHORITY(group-authority) ]

Please, give a look to this link to verify the syntax rules concerning the "userid" operand or "Syntax of RACF commands and operands"

http://publib.boulder.ibm.com/infocenter/zos/v1r12/index.jsp?topic=%2Fcom.ibm.zos.r12.icha400%2Fadduser.htm

 I  put here, to simplify   just a part of this link page:

 userid