Clamp the extruder on the top and bottom linear bearings of the X axis

Make sure all cables, except hotend cables, are running on top of the bottom smooth rod (between two X smooth rods). The hotend cable should stay under the bottom smooth rod.

Clamp the top of the x_carriage_back

Secure it with two M3x10 screws in top holes. Don't tighten them right now!

Finish securing it with two M3x18 screws in bottom holes. Don't tighten them right now

Gradually tighten each of the four screws while moving the extruder. Don't over tighten them.