Objective: Sew your first secured straight seams on scrap fabric, practicing threading, bobbin pickup, backstitching, and consistent seam allowance.
The MC6650 makes beginner sewing forgiving if you set it up in order. First, wind a bobbin: place thread on the spool pin, guide it through the bobbin-winding tension disc, wind a few turns onto the bobbin by hand, slide the bobbin to the right onto the winder spindle, and press the foot pedal or start button until full. Drop the bobbin into the top-loading case so the thread pulls off counter-clockwise and follow the arrows in the slot. Next, thread the top: raise the presser foot (this opens the tension discs) and raise the needle fully, then follow the numbered guides down, through the tension channel, up and into the take-up lever, back down, and thread the needle front to back. To bring up the bobbin thread, hold the top thread lightly and press the needle up/down button twice; the bobbin loop comes up through the plate, and you pull both threads back under the foot. Set stitch length around 2.5mm (the default straight stitch, pattern 1). Use the engraved seam-allowance lines on the needle plate to keep your fabric edge steady—the line marked 5/8" or 15mm is the standard garment seam. Begin and end every seam with 3-4 backstitches (press and hold the reverse button) so the stitching does not unravel. Let the machine feed the fabric; your job is to guide, not push.
Example: Take a 6-inch square of scrap cotton folded in half. Line the raw edge against the 15mm line on the needle plate. Lower the needle into the fabric about 1cm from the top edge. Hold reverse and sew backward 3 stitches to the edge, release, then sew forward in a straight line keeping the edge on the 15mm mark. About 1cm before the bottom edge, hold reverse for 3-4 stitches, release, and stop. Raise the needle with the up/down button, lift the presser foot, pull the fabric back, and cut the threads on the thread cutter. You now have a secured, even seam.
Try it: Cut three 6-inch squares of scrap cotton. Wind and load a bobbin, thread the top, and bring up the bobbin thread. Sew a straight seam on each square at the 15mm line, backstitching at both ends, aiming for a stitch length of 2.5mm. Compare the three seams and note which one stayed closest to the guide line.