How to test accessibility technologies in a website

Short background / Context

I'm a frontend dev newbie and would like to test that whether the accessibility of my and others' websites is good. So I am trying to find a screen reader for firefox or for ubuntu (linux) where I can hear the content read aloud by the program.

I've installed orca on Lubuntu though I couldn't yet set it up to read the websites aloud. I've also read and read through various websites but am still a bit confused.

Examples of these websites are wikipedia articles on screen reader, Vinux (a linux distro specially designed for these purposes). Also tried VoiceOver on an Iphone, which seems a very good feature (found on iphones accessibility settings).

Question

Any software I could install either on the browser or linux, or better any cross plattform / cross browser tool for reading websites aloud? Or approaches you may recommend to start getting into it?

I don't expect an all-throughout explanation but at least some guidelines.