While on a call in your system, click on "Warm Transfer" and it will allow you to add a call. Your are now on a three-way call!

If you hang up, it leaves the other two on the line. You have now performed a "Warm Transfer"

If you'd like to transfer someone to another person without being on the new call, you can use "Blind Transfer" and it will allow you to just forward them to the new number!

Hope this helps. I see a lot of upvotes here

I agree!