Blink integrates with Skype for Business to let you start a Skype call with any of your contacts, using just a single click.
Open your chat with the person you want to call and click the phone icon in the top-right of the title bar to start a Skype call with them.
If you can't see the phone icon, make sure you have completed your Skype username in your profile and that they have done the same. To find out how to edit your profile just click here.