Below are a few steps to set up basic security on a router,

Banner

Set Banner.

(config)#banner motd

Passwords

Set Secret enable password.

(config)#enable secret <password>

Set Line terminal passwords.

(config)#line <terminal> <number>
(config-line)#password <password>
(config-line)#login

Line Timeout

On VTY set timout out

(config-line)#exec-timeout <min>

Copy the Config changes

#(config) Copy running-config startup-config