Visitation

How do I enable visitation, do I have to have certain rooms?

On each hospital departments (the things on right side of screen) you can "zone" lounge areas, on which you plop down some visitors' tables. Just that. I suggest you place them near your regular wards.

Additionally, but not obligatory, you can place Gift shops (Admin dpt) somewhere near, so your visitors will purchase gifts for your patient.

Both getting visiting and receiving gifts will prop up your patients' satisfaction (One + mark each).

Not quite. Getting visited gives a (+ visited) bonus, but if you do not have a gift shop or the visitor does not buy one, you will also get a (- did not get gift) penalty.
By building the shop, you might gain the additional (+ got a gift) bonus to patient mood. So it is neutral, when you have only the lounge, a gift shop without one does not make sense and having both lounge and gift shop gives a ++ bonus.

hmm, is there a way one can facilitate visits outside via zoning? If not, I hope they update this in future so one can build a visiting garden/courtyard.

I do not believe so as outdoor props cannot be placed in indoor rooms and the lounge seems to count as one. Currently, the patients have no reason to go through a park although I'd like to have this feature very much.
You could do the following: place the lounge in a park area and have a corridor leading there with the same stones you place outside as pavement. Maybe this will work.

bummer. Yeah. I've let alone this DLC for now; seems really bugged. Frankly, I'm a bit concerned as this was the first true DLC for this game and man it seems to have been a really rough process. Read about a potential lounge bug this morning.

Well, the pharmacies and pathology work as intended with only two minor flaws:
- techs come to work with no needs fulfilled thus running off as soon as they get to their job and
- body fridges are pure decoration. I thought they would hold 3 corpses, but instead we must have those wide morgue tables to store more than one of them. Then again, hopefully we won't get more than one at a time.