Since the Bomb Factory Essential Tuner comes free with Pro Tools, it comes pre installed when you install Pro Tools, so there is no need to take any further steps if you have Pro Tools installed, which I believe is the only way that you can use this plug-in anyway. The interface of the software is straight forward and all you need to do to use it is make sure that you have your instrument plugged into the right input that you want to use it with. Each not will light up on the bottom to show you where you are at and there is a meter to show the amount of cents that you are away from the note you would like to get to. A manual isn't necessary for this plug-in and I'm not even sure if there is one.
While I have only used one of the Bomb Factory Essential Tuners at a time, it has always worked pretty well for me. I have the plug-in installed on a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I run the plug-in in Pro Tools of course since I believe it is the only software that you can run this with and I run Pro Tools 7.4 LE off of a Digi 002R audio interface. The only problem that I sometimes have when using this plug-in is the tracking as sometimes it is a bit off, but most of the time it works fine and this largely depends on your system anyway.
I've been using the Bomb Factory Essential Tuner ever since I got Pro Tools a few years ago and while I don't find myself using it all that much to tune guitars, it is nice that it is there if I need it. I usually just use a hardware tuner as I find it to work better than any software one and will be quicker, but when that isn't an option it is definitely great to be able to pull up a plug-in and use this guy. The free (with Pro Tools) aspect is great of course and I probably wouldn't have it if it wasn't free. All in all, the Bomb Factory Essential Tuner is a helpful plug-in that Pro Tools offers.