All sewing machines follow the same general outline when threading the upper tension thread. Generally, all machines have four main aspects of the upper tension. Different machine manufacturers have handled these same components using metal or plastic parts, but all machines contain a thread holder or spindle, thread guides, tension discs, and a threaded needle.
Every machine has a bobbin which is inserted into a bobbin case. Combining the upper thread with the lower or bobbin thread is what creates the machine stitch.
Make sure your bobbin is wound neatly and correctly. Holding the bobbin spool in one hand and the thread in the other, wrap the thread clockwise around the spool until it is about 2/3 filled with thread. Make sure the thread does not bunch or knot up.
Insert the bobbin into the bobbin case pulling the end of the thread through the slit in the side of the bobbin spool holder and leaving about 3 to 4 inches hanging out. Insert the bobbin spool into the machine until it clicks into place and the 3 to 4 inches of thread is hanging.
Place the spool on the spindle on the top deck of the machine.
Pass the thread through any guide-holes or ring eyes. Then pass the thread through the tension discs.
Pass the thread through any take-up arms and then thread the needle from right to left.
Newer machines tend to thread from front to back. Older machines, depending on the age, thread from right to left, with some versions actually moving from left to right. Sew some test stitches. Adjust the upper tension if necessary.