help with installing IP address update client

[unclebuk]

Hello, I have an AC88U and 68U router's with stock firmware and would like to install a dynu IP address update Client. I am not sure exactly what to do. The dynu website shows this code:

Below is the configuration file for Open Wrt:

config service 'dynu'
option enabled '1'
option domain 'YOUR-DYNU-HOSTNAME'
option username 'YOUR-DYNU-USERNAME'
option use_https '1'
option cacert '/etc/ssl/certs'
option use_logfile '0'
option check_interval '24'
option check_unit 'hours'
option force_unit 'days'
option update_url 'http://api.dynu.com/nic/update?hostname=[DOMAIN]&myip=[IP]&username=[USERNAME]&password=[PASSWORD]'
option password 'YOUR-DYNU-PASSWORD'
option force_interval '2'
option ip_source 'network'
option interface 'wan'
option ip_network 'wan'
option use_syslog '2'

Can anyone advise what steps are required to accomplish this? Use telnet for this??

Thanks in advance.
unclebuk