Add a drop of oil on your hook race on a top load bobbin machine.

Note: If you have never removed your bobbin case before, and aren't comfortable removing the bobbin case, please schedule a Quick Clean with me at TC's Sew Loved Machine Care. or with your local independent sewing machine service provider.

For a top load bobbin:

Remove the presser foot and the thread from the needle.
It's also a good idea to remove the needle as well, so it doesn't poke you and put in a fresh needle when you are done.

Remove the plastic bobbin cover from the needle plate & remove the bobbin

Remove the Needle plate: 
If your needle plate has screws, your machine may have come with a small device to remove screws in tight areas, or you can use a little stubby screwdriver, if you have one. 

If you have never removed your bobbin case before, take a picture of how it looks, so you will know how it should be put back in.

The bobbin case in some some machine models are easier to remove than others.

Some models have a bracket that needs to be swiveled to be able to remove the bobbin case. 

   

Gently grasp the edge of the bobbin case, and wiggle it out, but don't try to force it. 

Look in the bobbin area, if there is thread and lint, grab a cotton swab, pipe cleaner or small bush and clean out any debris from the area. Your machine may have a small hole in the center of the hook race that may have an oiling wick. If so place your cotton swab tip in the center twisting to remove any lint, but do not remove the wick.

When you have the bobbin case out inspect it, look at the metal tension guides and see if there is any thread caught between the guides, If you can grab an edge of the thread with tweezers to gently remove the thread, or use a very thin pin (like a silk pin) to move the thread without bending the tension guides so you can grab it with some small tweezers.

Look at the edges of the bobbin case to see if there are any jagged or broken edges from needle strikes. If there are, you may need to get a new bobbin case.

One drop of oil!

Place a drop of oil along the edge of the hook race, where your bobbin case sits. 

If your machine has a wick in the center of the hook, place one drop of clean sewing machine oil on the wick.

Then replace the bobbin case, making sure it sits fully in the edge of the hook race. Turning the hand wheel toward you, to make sure the bobbin case is riding smoothly on the edge of the hook race.

It can take a little time to get it back in, and seated correctly. Take your time.

refer back to the picture you took to make sure it's back in correctly.