This part of the guide shows you how to forward a domain to an IP address. CHnage the example IP address to that of your droplet:
http://www.one.com/en/support/guide/manage-your-dns-settings#ipaddress

Alternatively you could change your domains ‘Domain Name Servers’ to Digital Oceans own by following this guide:
https://www.digitalocean.com/community/tutorials/how-to-set-up-a-host-name-with-digitalocean

Edit: It looks like that it may not be possible to edit Name Servers(easily) for domains registered with One.com Source

Tanks for your reply, I will try to forward the to the ip address of my droplet!
I did follow the tutorial you posted, but when i get to step two i cant seem to find how to do it on one.com. I cant find where you change the domain name servers, anny ideas ?

Download: one-docs.com/forms/request-to-change-name-servers.pdf

And send it to : sales@one.com

Important !!! No digital sign

And than you can use DigitalOcean DNS