We are going to install a new fork.
First you put the lower slotted ring on the steer tube
Now put the steer tube trough the head tube and install the upper slotted ring and cover plate.
Now install all the spacers you need.
Push the fork up and install the stem. Now mark the upper edge of stem on steer tube.
Use a tool to fix the forks in to the vice and cut the steer tube about 3 mm below the line you draw.
Smooth the sharp edges with the file.
Now you have to install the star nut. I used a small screwdriver and a rubber hammer. Be careful not to damage the legs at the bottom.
Heavily grease lower slotted ring and upper bearing.
Install the fork and the slotted ring.
Put on cover plate, spacers, stem and top cap. Tighten the screw to the point where the fork has no play.
Tighten the bolts of the stem.