How to re-assemble key cylinder with the push button?

Please watch some videos following the links:

https://www.youtube.com/watch?v=WW8GuMoFAs4

https://www.youtube.com/watch?v=S3_xjgd-OsU

https://www.youtube.com/watch?v=1myWTJonDt0

https://www.youtube.com/watch?v=68c0gsCnvbM