how do I setup ARD to work across the internet?

There are a few good pages from which to start; also a search engine that does not

take you to odd sites or bad information could also be helpful to learn. A good book

from the Missing Manuals series for offline reading may also be a practical guide.

Also, the Help viewer in main Apple menu bar could locate more information.

Note: there are Client and Admin user products and levels involved in ARD.

• Remote Desktop - Apple Support:

https://www.apple.com/support/remotedesktop/

You may have to actually visit the remote computer to be sure the settings are correct.

Especially if that other user has no clues and the computer may need direct attention.

A pdf link to an article that may or may not be of help.

Apple Remote Desktop 3

See second search engine link below.

• Apple Remote Desktop: Configuring remotely via command line (kickstart) - Apple Support

My choice in search engine is one that supposedly does not track the search;

however a click on resulting links each could supply someone with information.

https://duckduckgo.com/?q=Using+Apple+Remote+Desktop&t=ffsb

https://duckduckgo.com/?q=Using+Apple+Remote+Desktop+setup+over+internet&t=ffsb

Good luck & happy computing! 🙂

ARD isn't necessary for doing remote screen sharing, the standard screen sharing tool built into OS X will work for this purpose. Either Messages and screen sharing can often be enough, or the integrated Screen Sharing client can be used to share the desktop when needed.

Figure out Messages and screen sharing and test that, or use some screen sharing service; maybe TeamViewer or an alternative, either commercial or potentially for free if the associated licenses permit your intended usage. That'll be far and away the easiest approach, here. Add the Messages app to the login, and work through the sequence to accept or to request the required screen sharing.

Otherwise — if the remote end isn't assisting with establishing the connection — doing remote access can mean figuring out a VPN and a VPN server, and likely setting up dynamic DNS (DDNS) to allow you to get the IP address of the remote site, and likely all operating in a firewall gateway box that you've acquired for the remote site. DDNS is cheaper than static DNS, and the DDNS services — which get you from a host name you can use to whatever IP address the firewall is at right now — are cheap or free.

To use your own firewall, the ISP modems will likely have to be switched over into their bridged mode, as that gets them out of the way and allows your gateway box to control the network link without NAT getting in the way. ISPs are only material if they block the particular network access involved, or don't allow the modem to be switched into a bridged mode.

I tend to use the low-end ZyXEL ZYWALL USG series boxes here, though those expect some familiarity with IP networking and VPN services. No financial ties with ZyXEL, other than having purchased gear from them. The ZYWALL boxes support DDNS, not that I've had need for that with the use of static IP addresses.

If your father is logged into an iCloud account, you can start a screen sharing session by invitation. Hit Cmd-K in Finder. To make the URL, use "vnc://" and then append the AppleID (Eg: dad@icloud.com). It starts in Observe mode, so you will need to click on the Control icon in the screen sharing toolbar. It will send a second notification so your father can grant control.