Start by making a mess.
That’s right, the key to starting is making a mess. I always tell my clients it’s going to get worse before it gets better, just one thing at a time.
When I was a kid I made a fort/spaceship out of cardboard and was fully armed with an arsenal of nerf guns and stocked up with snacks for my imaginary journey to some yet-to-be-explored planet or jungle. How did I travel there? In a giant scribbled upon refrigerator box, I connected to my bunk bed of course.