Adding sidebar with widgets using coding

Hi everyone,

I would like to add some custom sidebar with widgets onto some of my posts & pages. However, I wish to have different widgets on them, any idea how to do so? Example sidebar A with widget A, sidebar B with widget B and so on.

I had tried looking for sources but I was unable to understand the coding and the instructions. I had saw https://www.ads-software.com/support/topic/programmatically-add-widget-to-sidebar?replies=5 but I got no idea what it is about.

P.S. Sorry if I posted at the wrong place.