With a Google Docs opened, choose
Tools -> Script Editor.
For use the script it must be encapsulated in a isolated (out of a class) function.
See how to use the Google Script Apps in doc.
- Just click on
run->Review permissions(to authorize the script to make changes in your document); - In the open window choose a google account -> click on
Advanced->Access ...(unsafe)->Allow.
Note: to access all projects access this link.