Unscrew the four screws securing the bottom plate of the sewing machine arm and remove the plate.
Locate the screw adjacent to the bobbin and remove it. Then pull out the looper with your fingers.
Insert the new looper into the space where you just removed the old one. Guide the looper with your hand, aligning the ridges on the back of the looper with the corresponding grooves until the looper locks into place.
Add a few drops of lubricating fluid to the looper shaft. You should use Singer brand machine oil, but other brands of sewing machine oil will suffice.
Adjust the looper with your hand so it is very close (about 1/5 inch) from the needle.
Replace the screw.
Reattach the plate and insert the four screws you removed in Step 1.