It is true that the process of creation begins long before the first mark is made. But, the mark is the commitment. The mark makes it real.
I grew up with artists and I often agonized over how to begin a drawing or painting. "Draw the first shape you see, " I was gently advised.
That first shape you see, it is your focal point. Once it is established your work will build and develop into a finished product that is true to your inspiration.
Make your mark today, and keep going.