Take three M3 x 40mm bolts and slide onto each of them an M3x2mm spacer.

M3 x 40mm bolt

M3 x 2mm spacer

Fix these bolts onto the spool holder and fasten them into the back of the extruder motor, where the three bolts were removed in the previous step.

Spool Holder

M3 x 40mm bolt and spacer

Match the orientation of the spool holder shown.