You can find this setting in the wireless security section, where you'll select which type of encryption to use and then enter a passphrase of at least 8 characters -- the more characters and the more complex the password, the better.
Ị nwere ike ịchọta ọnọdụ a na mpaghara nche nchebe, ebe ị ga - ahọrọ ụdị ụdị ntinye nzuzo iji tinye ma tinye pasphrase nke ọ dịkarịa ala 8 odide - ihe ndị ọzọ ka ederede na mgbagwoju okwuntughe, nke ka mma.