I am trying to run wireshark in linux using sudo, but was told: i am not in the sudoer files. So I must edit this file to add my own user into this file. Steps as follows:

1. su to root:  su-
 2. open sudoers:  visudo /etc/sudoers
3. add my user name:  testuser ALL=(ALL) NOPASSWD:ALL
    This lines means that the user "testuser" can execute from ALL terminals, acting as ALL (any) users, and run ALL (any) command.

The detail is in paper:  http://www.go2linux.org/sudoers-how-to