I have forgotten how to thread it

Perhaps this video will help. Not your model, but there are similarities that will help. NOTE: Before threading the upper thread, RAISE the presser foot so the thread will seat properly in the tension disk.
Kenmore 158 17550 Sewing Machine Tutorial
How to use your basic sewing machine 1

Before trying to sew, test your machine by turning the handwheel manually. If it is hard to turn, parts do not move or when you try to run the machine, it bogs down and does not operate, then you need to do some maintenance since the oil has probably dried out while in storage:

Treat your machine to a good cleaning and some Fresh "good quality" sewing machine oil (not 3-in-1, WD-40, cooking oil, or stinky brown stuff from the bottom of the sewing basket). Do not oil rubber, leather, plastic, or belts as the oil may damage them. Look for little holes that are oil ports. Apply 1-2 drops in each. Then gently rotate the handwheel and apply a couple drops every where that metal rubs on metal. Don't forget the bobbin area!

The following videos may help or you can search YouTube for other videos.

https://www.youtube.com/watch?v=xh4SeRdqBiw

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I think it will help if u explain by pictures please for how to thread brother sewing machine vx 1450

Hello :

Here I'll tell you how to thread a sewing machine . Just let me know if that worked or not to provide another help .

1. Raise the needle to its highest position by turning the handwheel toward you.
   
2. Raise the presser foot. This will allow the thread to easily pass through the threading points and will prevent the machine needle from becoming unthreaded when you begin to stitch.
   
3. Place a spool of thread on the spool pin located at the top of your sewing machine. If the spool pin runs horizontally, secure the spool of thread with the cap provided.
   
4. Take hold of the thread end and pass it through the designated threading points on the top of the machine casing, then down toward the tension assembly. The tension assembly is located on the left side of the machine and controls the flow of thread.
   
5. Take the thread under the tension assembly and back up through the next threading point at the top left of the machine. Make sure the thread has passed between two tension discs as well as the hook that may be attached to the left side of the tension dial.
   
6. Push the thread end through the lever at the top left of the machine, if applicable, and down through the threading points at bottom left and above the needle.
   
7. Thread the needle from the front or back of the needle. The threading direction will depend on your machine type.
   
8. Pull a few inches of thread through the eye of the needle and pull the thread to your left.
   
9. Insert a wound bobbin into the machine, if necessary, and close the throat plate. A few inches of bobbin thread should be pulled out to the right and sticking out from under the closed throat plate.
   
10. Take hold of the thread that has been threaded through the machine needle.
    
11. Rotate the hand wheel toward you until the needle disappears into the bobbin case.
    
12. Keep holding on to the thread and move the hand wheel so the needle is once again at its highest position. As the needle rises, a loop of bobbin thread will come up as well.
    
13. Pull the thread out toward your left to draw the bobbin thread loop further out of the bobbin case.
    
14. Let the top thread go and pull the bobbin thread up until the end comes up. Pull the top and bottom threads under the presser foot and to the back and right of the machine.
    

• Spool Of Threads
• Threaded Sewing Bobbins
• Sewing Machine Needles