How to change tempo to different sections of song

[loki777]

I want to change the tempo to different sections of my song but am unable to I saw on YouTube to click the master and press a which didn’t work. I notice some hot keys do not work like pressing x and z to zoom in and out also is there something I have to enable so these hot keys work?

[chapelier fou]

You can click the "automation mode" icon which is next to the "automation lock" (a lock icon) around the top-right corner of arrangement.