Install different python version in self hosted Ubuntu Agent

Question

I am trying to install version 3.6.15 of python on my self hosted Ubuntu 20.04.3 LTS machine (GNU/Linux 5.11.0-1022-azure x86_64)

I have downloaded the agent and it works, but we need a different version of python on it.

I am aware of the python having to be put into the _tool/version/x64/ folder to add to the toolchain so you can use the use-python-version task.
However I am not sure what files are to be put in the x64 folder of the python version. I am not very knowledgeable in Linux environments nor pipelines, and neither is this doc since it points at an installer for windows and not ubuntu nor helps me understand what I am meant to do in terms of commands.

Please if anyone could help me deal with this, I've been on this issue for days and it is super frustrating to have such a hard time on a such apparent easy task.