On rear of engine above offside driveshaft, easiest way is to follow the thick starter cable from the battery to it.
A shit of a job to do, on ramps anyway, you will be best removing offside driveshaft.
Common problem on these auto's, done two on me own, but third one I sealed the whole starter housing, oil seesm to find it's way to the rear around the starter, and even seeps in the braided wire between solenoid and motor itself.
A lot say FORD only design, it is in fact a rip off of a LUCAS design, and LSUK were cheapest when I got mine, ford decided to change the brush box design on theirs meaning you can't buy brushes, but you can use washing machine ones cut down.
tabetha