I Haven't Done IT!!!!

IF the window slides into the regulator, this is what I'd try...
Put on the outer fuzzy first.
Then stuff the window in, making sure the lower stop is out, allowing the window to drop below the edge.
Then install the inner fuzzy (is it on the door or the inner panel?)
Then stick in the regulator collapsed so it fits in the hole.
Then get the window on the regulator.
Then bolt the regulator to the door.
Roll the window up and install the lower stop.

Some windows bolt to the regulator. If yours is a bolt-on,
Bolt in the regulator loosely, the set to the point where the regulator/window bolt align with the holes in the door. Remove the regulator.

Put the outer fuzzy on.
Stuff the window in, with the bottom stop in place.
Inner fuzzy (if it's not on the inner panel).
Bolt in the regulator and raise the window to the holes and bolt up.

The window almost always goes in at an angle, nose down, then is rotated into the front and rear guides. If one is removable, it's best to get the window into position, then bolt it in loosely.

Then it's the joy of adjusting the window so it fits and seals. You did lube everything, right?

One of those big suction cups use for bodywork or glass installs is useful...It will keep the window up as needed.