Important Disclaimer
Modding Final Fantasy XIV or using tools that hook into it (like ACT) are against the Terms of Service. However, unless the tool/mod/plugin allows for an explicit advantage over other players (cheating), Square Enix turns a blind eye to this type of activity. However, they will not tolerate it being talked about or mentioned in-game. As such;
Modding in this game follows a simple rule: "Don't ask, don't tell." Don't ask if someone is using a mod or tell other people that you're using mods. Especially don't harass other players based on information gathered from a mod (such as mentioning their DPS). As long as you keep this in mind, you'll be fine modding.
Requirements
There's a bunch of stuff we need first to make all of this work. That includes a launcher, installing plugins and downloading some assets.
XIVLauncher
First we need this custom launcher that enables plugins and has other neat features, like skipping password input, faster patching speeds etc. Their website has all the information on how to install and more, so please visit their web and install XIVLauncher.
Assets
We also need two fonts and a bar texture to fully embrace the ToxiUI style. All of these can be found on this GitHub page.