To hit the ground running is a way of saying that you are well prepared, so that when you begin doing something you already know what to do - you have an advantage over others who are not so well prepared.

It's an expression. For example, if you're running late for work & you have to "hit the ground running" when u get there, it mean you have to start working furiously fast to catch up from being late just so you can get to the level of work you should have completed by __o'clock. :-) Hope that helps.