This video is embedded from Youtube and here’s the original one.

0:00 Introduction
1:05 Create a New Customized Field
1:40 #1 LOWER/UPPER Function
3:05 #2 CONCAT Function
4:35 #3 REGEX_EXTRACT Function
6:05 #4 REGEX_MATCH Function
9:30 #5 CASE Function
13:20 Summary

Resources: 
All Functions: https://support.google.com/datastudio/table/6379764?hl