You shouldn’t animate the actual root bone except for little cheats here and there or if it is an ‘in-place’ cycle (where the root moves forward)
So where do you position it at the start?….It depends.
I chose the most logical position for the shot. In your case, I would either position it where he would be at frame 1, or on the ground at the bottom of the steps (if he is doing a lot of animation down there)
You can leave the root bone where it is and keep animating.
But it is also possible to snap the root bone to a new location over 1 frame (but just keep an eye on the switch)
This might be useful to you if you want to add a walk cycle (that you have already animated) to the end or whatever.
You will need to keep an eye on this switch and keep your head around what is going on (the GE will look crazy at that point).
I haven’t shown how to do that in any of the videos, but maybe you can get the gist from this description. (hopefully anyway haha)