HO do i set up a ring topology with Ubiquiti switches (Ubiquiti UniFi Switch US-48-750W)

What do you mean by a ring topology of switches ?

To get 400Ft between switches, you should be using Fibre as the max run length on Copper is 328 ft https://en.wikipedia.org/wiki/Category_6_cable

Cabling considerations aside, if you want to set up something like this

[sw1]------[sw2]----[router/fw]
  |          |
  |          |
  |          |
[sw3]------[sw4]

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you can cable up the switches using the SFP ports for fiber or let's say port 47-48 for copper (if within 100m).
Spanning tree will disable one link to temporarily break the loop, if anyone disconnects/cuts a cable spanning tree will re-enable it and the show goes on.
I'd set it up for RSTP protocol, make the switch closest to the router/firewall the root of the spanning tree (set priority to 0).

Some switches provide cool ethernet ring protection protocols instead of spanning tree, but those are typically for carrier metro-ethernet deployments.

I want to use Fiber between the switches as the distance does not permit copper...

In that case do use the SFP modules on the switch.
I'd go with multimode fiber and 1000Base-SX optics, the official Ubiquiti one is UF-MM-1G, but according to their docs they do work with pretty much anything you have on hand:
UniFi - USW: Which SFP Modules Can be Used

great!.....Also wanted to know that is this is possible ..... on the main / master switch that would be part of the ring in which 2 of the SFP ports will be occupied a part of the ring topology ..... can i also add  an additional switch to each of he 2 other SFP ports ?  If so would the master switch see all the switches as one network  ?