Ignorant PC gamer question:

This is something i'm really apprehensive about.

I fervently hope that while you are outside the fort there will be a general chat

Yes, Origin works kinda like Steam, just add your friend to the Origin itself and then you are good to go.
I think it will work just like in ME3 when you can invite you friend from a game menu or "Origin in game" menus.
Cheers

ok, so on Origin, someone would need to know your username, yes?
And people could share those the same as people share gamertags on a console?

::Fires up Origin, looks at friends list:: Well there's my problem, no friends.

"Real knowledge is to know the extent of one's ignorance. "

Confucius

Sadly, I do not yet know its extent... 

The Origin friends list works very similarly to the console friends lists. You can send them messages, invites, or even join their session directly through the friends list if the game supports it and said friend has space + hasn't set the session to private or invite-only. There will also be the standard in-game matchmaking and invite features. You can also change your status to invisible/appear offline if you just want to fly solo or don't want to be bothered by anybody. This is how I am about 90% of the time I'm signed in to Origin.

That said, Discord will probably be the main way people handle larger groups and/or clans because it's such a ubiquitous platform, and its voice chat will almost certainly be much better than whatever gets included in the game.

The only downside at least back with Mass Effect 3 is Origin capped out at 100 friends and back at the launch of Mass Effect 3 people seemed to want to add one another from good groups a lot of the time. Dragon Age: Inquisition and Mass Effect: Andromeda I didn't play the MP enough to really know if the cap changed.

The cap was upped to 2,000 some time in mid 2016.

In The Division when you log in via Uplay it automatically tells you who is playing the game from your friend list. If you have no friends playing when you are in game there is an in game general chat box that you can type messages into saying that you are looking for people to do X mission or just free roam but it also works on proximity so if you are standing next to someone you can voice chat and review players stats.

Alternately you'd just go to where a mission starts and you can choose to play or replay it and choose whether you want random players to join for the mission and you can wait for people to fill the team or just start and people can join at any time during the mission. Most of the friends I made were people I met randomly playing missions again who then would friend request you or via chat ask you to friend them. I also met people on the forums who I then friended and ended up doing missions with.

If you login and friends are playing you can also open a menu and it gives you an option to automatically teleport to their location whatever they are doing.