Hit the ground running
Definition 1 of 3
Pro Tip 1/3Immediate Action
The phrase implies quick and energetic starting, not gradual preparation. 
She hit the ground running and finished the task in record time.
Pro Tip 2/3Energetic Approach
Shows enthusiasm and high energy right from the beginning. 
Joining the sales team, he hit the ground running with remarkable zest.
Pro Tip 3/3Not Literally
It's metaphorical for quickly starting, not actually running. 
As soon as she arrived, she hit the ground running with the new project.