How to: Merge two existing voice calls in Skype for Business for Windows

Instructions

1. From either of the active call windows, click the "More Options" button (three dots).

example screenshot

2. Click Merge This Call Into, and choose the call you would like to merge with.

example screenshot

OUTCOME

Your calls will automatically be merged into a single conference call. You may disconnect yourself from the call anytime you wish, and the call between the other parties will continue.