For SQL statements, you want to grant them at the database or table level.
Please see the SQL Reference Vol 2, and look at the GRANT statements. In order for a user to be given DB2 authority, they first need to have a userid and password set up in the Linux operating system.
If the users will connect (telnet, ssh, etc) directly to the DB2 server and logon, then they need they need there profiles set up in the same manner as the instance owner to initialize the DB2 command line environment. I believe that it is located in .bachrc for the bash shell.
If they will access the Linux server via a remote Windows client (probably the preferred method), the you need to install the DB2 client (free) on each Windows machine, and catalog the remote node and database (that exists on your Linux box). Even for remote users, in order for them to be given DB2 authority, they first need to have a userid and password set up in the Linux operating system.
If they are learning DB2 database administration skills, it might be better to give each one their own database, and give them dbadm authority for their own database.