Required Internal Authors to Collaborate and Work in Same Project

[#1]

Hi Team,

In the initial phase, i have acquired RoboHelp 2019 for Individual Contribution Role. After a year, the documentation requirement has risen up.  Now, we require 3 authors' contributions to the same project. 
Now we need your guidance. Those requirements are:

1. How to Setup? (what all require)

2. Is there anything we have to purchase add-on? etc.,

[#2]

Hi Team,

In the initial phase, i have acquired RoboHelp 2019 for Individual Contribution Role. After a year, the documentation requirement has risen up.  Now, we require 3 authors' contributions to the same project. 
Now we need your guidance. Those requirements are:

1. How to Setup? (what all require)

2. Is there anything we have to purchase add-on? etc.,

[#3]

You need source control. I can't help you with that but your developers should be able to assist. There's nothing you have to purchase on the RoboHelp side to make it work with your source control. Your delvelopers will be able to advise you on what is needed on the source control side.

Hopefully someone with source control knowledge can add to this thread?

You haven't said whether you are using 2019 Classic or the new UI. If the latter, the RoboHelp Reimagined sample project points to the help on Adobe's site.