I hope this comment doesn't count as spam. But I just want to let you know that I have made a GUI frontend (called ProxAllium) for Tor, it setups up the `torrc` configuration file for you, this might make the process of managing tor more user-friendly. It is totally open-source and isolates all of the configration from rest of the system, so it is fully portable as well :)
Another piece of advice is that I recommend using `tor` from the Tor Browser Bundle, as it will make updates easier than manually checking for updates in the expert bundle. ProxAllium can guide you through the setup process for both the Expert Bundle and the Browser Bundle!
If you do decide to use ProxAllium, you will have to first do an initial run where it will generate all the configuration files, and then edit `config.torrc` with your own options related to hosting the relay. u/system33- has already given you some excellent instructions on how you can configure the relay.
Thank you for considering to run a relay!
I am not sure if older versions of Tor had the ability to route all of your traffic, but Tor does indeed come in a standalone version, it is well hidden in the website so it is hard to find it without knowing what you are looking for: https://www.torproject.org/download/tor/ (it is called the "Expert Bundle")
Tor is a command-line program so you will have to invoke it manually, but I have made a program called ProxAllium which presents you with a nice GUI to start Tor and manage it, check it out if you are interested :)
Once you have Tor running, you will have to manually configure youtube-dl to use the local SOCKS5 proxy (the proxy details are neatly displayed in ProxAllium).