Adding your employees, agents, salespeople, staff directly
You can add employees to babelforce manager app directly by following the simple steps outlined in this article:
That is in a section explaining stuff about Users, agents and roles.
Feel free to start by adding agents directly, since you can always change them later or delete and replace from a source. So you won't cause any problems testing with direct agents.
Syncing agents from another source
If you want to create agents automatically by syncing from another source, then you can check out the particular integrations that can be used as agent sources: Integrations
Here is an example of how that works for one ticketing system: