All you need to do is connect to the user directory like (AD or Local Group), then assign each user a role.
Have a look at the link for help.
There are a number of ways to do this depending on your system requirements.
1. Create a UDC(User Directory Connector) that syncs with LDAP or AD.
2. Create a UDC that syncs data in from and Excel Spreadsheet
3. Create a UDC that syncs local users on the server.
There are a couple of other UDC setups you can also do. You can use more than one.
I have been using option 2 for my Development Server. Once you have the spreadsheet setup the process is pretty easy.
Keep in mind that the UDC only syncs attributes into Qlik. It does not authenticate. By default Qlik uses Windows authentication.