PostgreSQL has to be installed from a folder that Resolve installes on you system before you can use Project Sharing. Hopefully I can get behind my system so that I can get you the extract folder to look in to install it.
"MY MEDIA/PROJECT MOTTO: If you think three copies of your Media or Projects are enough. Take a moment to place a value on them and then maybe add two more. Hard Drives are now stupidly cheap. A RE-SHOOT AND YOUR TIME AREN'T."
On which ever machine is running your server, you would open the Resolve project manager program and create a new postgresql database on that machine. Use the default username and password...do not use a username and password that is associated with your personal computer login information...just use default option that comes up.
The ip address will come up as 127.0.0.1 leave that alone, as it indicates the local machine will be used. (the machine running the server)
once the database is created, enable sharing on it. Without sharing enabled, no other machines can access it.
On your second machine, go to the database area and select new database...Connect. Type the name of the database you previously created and shared in the name column.area. This must be identical to the name on the other machine. You will also have to know the ip address of the first machine. (both machines must be on the same network setup) You can't use 127.0.0.1, as that will again point to the local machine...the machine you are on right now... You need to point it to the original machine which is running the server. So something like 192.168.0.???
Username and password stays as the default.
Click "add" and if all is setup correctly you will join the shared database.