I search a lot of and the way are soo dificult, and I don't know way.

Yo can configure it in a simple way.

#Install ddclient to manager dyndns.
yum install ddclient

#Add the configuration to the config file. You have to edit the file (Be carefull!!!!, only edit this).
#For security we back up the original file

cp /etc/ddclient.conf /etc/ddclient.conf.back
nano /etc/ddclient.conf

#Search the sentence below and change it.
#use=if, if=eth0

Del de "#" to activate it, next change the if interface if you need, In my case I havea ppp0 conection (or ppp1 if you have multiple ppp conections).
use=if, if=ppp0

#Next Search the login options and del the "#" to activate it, put the correct dyndns user and password
login = your_dyndns_user # default login
password = your_dyndns_pass # default password

#now we configure dyndns and the hostname, del the "#" to activate it.
#In the first 2 lines only del the "#".
#The 3th line is your dyndns hostname
server=members.dyndns.org, \
protocol=dyndns2 \
your_hotname.dyndns.org

#To exit only have to pres Ctrl+x, and then press Y to write the changes.

#Start the service and test it.
service ddclient start

#You can see the service status with
service ddclient status

#The last step is add ddclient to auto start (When you turn on the PC).
systemctl enable ddclient.service

#To see if all is working, only do this
ping your_hotname.dyndns.org
#If you se that the ip is the same that your ppp ip, all is fine.

Enjoy it!!