The most fundamental requirement for proper sewing is a threaded needle. Machine sewing, like hand sewing, begins with a proper path from the thread supply through the eye of the needle. Correct threading means following the instructions for your make and model of machine, ensuring correct tension on the thread for balanced stitching through your fabric.
That said, if you are looking for some help, here are general instructions for how to thread a sewing machine.
Standard thread used on home machines is wound on spools with the threads lying parallel to the spool ends. This makes the thread feed easily from a vertical spool pin without catching in the notch that holds the thread end when the thread is not in use. If your machine has a horizontal spool pin, be sure to position the spool so the notch is facing to the right (away from the needle side of the machine and toward the flywheel side of the machine.) This prevents the thread catching in the notch and breaking as it feeds from the spool.
To use cone thread, which is wound diagonally to feed from the top of the cone, you will need a stand to hold the cone behind the machine. Thread stands have a pole with a loop at the top to carry the thread up from the cone. Do not try to balance a cone on a vertical spool pin.
Pass the end of the thread through all loops and tension disks, following the diagram in your sewing machine owner’s manual if possible. Most new machines have arrows on the machine itself to indicate the correct thread path. Before threading the needle, check for correct threading by lowering the presser foot and gently tugging the thread end. If you have properly threaded the machine, there should be some resistance to your pull. If there is no resistance, you need to check to see if you missed a station on your thread path. If all is well, lift the presser food (releasing the tension) and pass the thread through the eye of the machine needle from front to back. Make sure the thread is not wrapped around the needle, but passes straight from front to back through the eye.
In professional workrooms where thread is frequently changed, the operator does not unthread the machine. Instead, the old thread is cut near the spool or cone and new thread is tied on with a square knot or a weaver’s knot. Then the needle is unthreaded and, with presser foot up, the thread end is pulled until the new thread has passed through all the stations and is ready for the needle. Cut the knot off and thread the end of the new thread through the eye of the needle.
Once your machine is properly threaded on top, it is ready to run smoothly through the machine, locking with the bobbin thread to produce smooth, even lines of stitching.