limit IP to access wp-admin

Under /wp-admin/ add .htaccess

AuthUserFile /dev/null
AuthGroupFile /dev/null
AuthName "WordPress Admin Access Control"
AuthType Basic
<LIMIT GET>
order deny,allow
deny from all
# whitelist Syed's IP address
allow from xx.xx.xx.xxx
# whitelist David's IP address
allow from xx.xx.xx.xxx
# whitelist Amanda's IP address
allow from xx.xx.xx.xxx
# whitelist Muhammad's IP address
allow from xx.xx.xx.xxx
# whitelist Work IP address
allow from xx.xx.xx.xxx
</LIMIT>