I plan to install the Mishimoto Coolant expansion tank on my 2015 mustang gt. I know I’m going to have to bleed the coolant system to get rid of any air but where is the bleeder screw located to do so??
There isn't one. The expansion tank is the highest point in the system so there's no need to bleed anything unless you plan on emptying the coolant from the rad first. Personally I'd just pop off that lower outlet hose from the reservoir and put a pan/jug there to catch what comes out of the factory one. Some mess is inevitable but a lot less time consuming.