how to edit user limitations

Hello I am new to apple and have just got a imac, I love it so far. I have set it up for use by multi users (family), I am the admin account and others have standard accounts. I noted when I set them up I could change what they could do when they log in but didnt do anything about it then. Now I would like to limil what they can do but can;t seem to find the limitation tab now, can anyone help? I have accessed user accounts but it is just not there?

Thanks

Mr_Wal