If you actually want to strip and service it, then is easiest done still attached to the hub.
Hammer and punch in one of the dimples. Hit in a clockwise direction as you look at it (left hand thread). Unscrew the front race and catch all the balls, shim washers and springs etc as they fall out.
Clean it up - if not too badly pitted then can just be rebuilt (bearing surfaces do not need to be perfect - but any chipped teeth or pawls then bin it). If you are scrapping it at this stage, then grip the remaining centre bit in a vice and unscrew like you would a normal BMX freewheel (right hand thread).
Quite fiddly but not impossible to rebuild. Minimum amount of grease to hold balls in place. Only oil NOT grease on the pawls (or they will stick).
Edit - nickjb beat me to it! Except he got the thread-hand wrong