Co-Regulation: Stepping in with soothing, responsive interactions to help a person be able to regulate their emotions.   OR Borrowing the ability to attain a regulated state from another person who is emotionally regulated and responsive to our need for assistance.

First – you need to regulate yourself.  

Second - let them borrow some of your regulation.  

The final step of regulation is to actively teach children how to regulate themselves, giving them tools to use.

Resources:

Mona Delahooke https://monadelahooke.com/

Deb Dana https://www.rhythmofregulation.com/

The Whole Brain Child- Dr. Siegel and Dr. Bryson