To  password protect privileged exec mode on your switch, issue the following command in global configuration mode

enable secret my_password

if you are running an old ios and enable secret is not recognized then issue

enable password my_password

and encrypt the password

service password-encryption

next secure the virtual consoles

line vty 0 15
password_my_password
login
 

and finally the console

line con 0
password my_password

do not forget to issue from privileged exec mode

copy run start

to save your configuration

reload the switch and test