In order for you to manage DNS with DigitalOcean, you will have to save your DigitalOcean API key to your Ploi account.

Head over to cloud.digitalocean.com and log in. After that, press the "Generate New Token" button:

Next fill in a token name, set the desired expiration and select "Custom scopes". Then select the scopes below, you only need to have the "Domain" scope added:

Press "Generate token" and you'll be presented with your token:

Copy this token and go to your Ploi profile to Integrations, scroll down until you see DNS providers, and enter the token there.

You will now be able to attach your sites to your DigitalOcean API key and manage DNS records. To do this, head over to your site in Ploi and press the "Settings" tab, next scroll until you see "DNS Settings" and enter the right provider, and the domain name. Now a DNS tab will show up and you'll be able to manage DNS records directly from Ploi.