How do you attach metal washers?

The 4.5mm and 6mm eyes come with their own unique metal washers.  Here is how to apply them.
The stem of the eye is inserted in this side of the washer:

Not this side:

Insert the end of the stem into the washer, and then use both thumbs to push the washer while using your fingers to push the eye down into the stem.  As the stem is pushed through the washer, the 2 small metal arms expand, holding the eye stem in place like this:

Tip:  If you do not have the hand strength to push the washer onto the eye stem, place the eye stem side up on a hard surface like a counter top, put the washer on the stem, and then press down with your thumbs on the washer.  It should slide on easier for you this way.
Have a click pen handy?

Remove the ink well from the pen, and the end will fit over the stem.  Use it as a tool to press down on the eye stem like this:

The pen trick will only work for small eyes from 4.5mm to 6mm.  For larger eyes, use the handle of an interchangeable screwdriver.  Fits perfectly and it’s ergonomic.