Are you currently using a LMS (learning management system) to host your company's courses? If so, what is is hosted on? Ideally you would probably like to have the community built on the same platform as your LMS, that way users only have to sign in once. Worst case scenario you can build an outside online community and then create a trigger that transfers the log in data between the different cms.
How many people is it? The most simple solution for an online community is Slack. Their product is really easy to use and has an app.
However, if your goal is to create a whitelabeled solution with your logo, then you could look up a "Facebook clone".