So you have Skype Desktop and want capture your conversation and stream it. Ok, no problem.
Step 1: Install SoundFlower.
SoundFlower is very popular open-source sound driver for macOs.
So download package from DOWNLOAD LINK and install it step-by-step. Please use right-click menu for open package (see picture)
Step 2: Setup Skype
Please open Skype (desktop of course) and open preferences dialog. Select "Soundflower (2ch)" for "Speakers"
Step 3: open JustBroadcaster and connect headphones to Mac
a) Add audio devices "SoundFlower (2ch)" and "Built-in Microphone"
b) connect headphones to Mac and turn-on icon "Headphone".
So you can call into Skype and start stream.
How to testing without stream:
1) press "Rec" button
2) call to "Skype test call" and say something
3) press "Rec" button again
4) go to "Movie/JustBroadcaster for ..." and open last recorded file for check.
NOTES: for use Skype without JustBroadcaster please open Skype->Preferences and change "Speakers" to "Built-in Output".