Can someone tell me how these teleport doors work please? Do I need to be in edit mode to position them?

Yes.

you buy them in store like furniture. WHEN bought only buy 1 you get 2 doors in every purchase. for a matched pair.
only buy 1 pair at a time before placing them, so you don't have 30 doors, 15 pairs that you have to figure out how to match.

You place them in rooms like furniture, place one whichever direction and spot you want.
Then take the other to the room you want to connect directly to. place that one.

Thank you so much

Can only buy 1 each purchase then it says the other teleport door is unavailable after I place two of them in respective homes? Maybe a glitch?

Usually when that has happened to me it's been because I had 2 sets of doors and got them mixed up like the following:

Pair 1. Doors A + B
Pair 2. Doors C + D

I placed door A inn a room and then door C or D in the room thinking they would connect. But they won't.

So, if I were you i'd drop one door in each room, until you have none left in your inventory because you might have 2 sets, or even just 3 doors..
Once in rooms you can use the doors to get your sets back organized, only pick up a set at a time.

If you've checked that^^ already. Then yeah you should submit a ticket to get it sorted.

Thanks I'll try that and see what happens.

Thank you they both work now! Have a great day!

Awesome. lol.
You too.