TL;DR How do I enable extra addons when Odoo (Community Edition) starts up?

Hi folks, I'm running Odoo v10 (Nightly Build), installed via these instructions (Editions -> Debian -> Community):
https://www.odoo.com/documentation/10.0/setup/install.html

I'm running Lubuntu v16.04.2 (basically Ubuntu).

Odoo v10 Community works great, but I'd like to load some other Addons which appear to be bundled with the nightly build but not necessarily enabled - and it doesn't seem like they can be enabled with the "Apps" Web front-end.

A couple of interest are "base_vat" and "pos_discount".

Although the POS front-end can discount line by line (input a new price or discount by percentage), I'm not convinced these current features are what pos_discount offers. The addon page for it is rather vague but it appears as if I should be able to discount every line (an entire list of items) at once, so I'd like to activate "pos_discount" if it's not already by default.

"base_vat" is a recent request from my Manager to have enabled, which I'm not familiar with, but I can confirm it is located in: /usr/lib/python2.7/dist-packages/odoo/addons/ (along with "pos_discount") - but again it's apparently not enabled and I do not see an associated App on the web front-end for it.

I have been trying to find a way to launch Odoo manually with extra command line arguments to enable these Addons, but nowhere on my system can I find either "odoo.py" or "./odoo-bin" to even attempt it, as per this page:

https://www.odoo.com/documentation/10.0/reference/cmdline.html#running-the-server

Many thanks for your support.